c 

MWT 


VOLUME  2 JULY,  1905  NUMBER  3 


BULLETIN 


OF  THE 


Mississippi  Agricultural  and  Mechanical  College 


A PRELIMINARY  REPORT 


OP  SOME  OF  THE 


CLAYS  OF  MISSISSIPPI. 


AGRICULTURAL  COLLEGE,  MISSISSIPPI 


Published  by  the  Mississippi  Agricultural  and  Mechanical  College. 
Issued  Quarterly. 

Entered  as  Second  Class  Matter  at  Agricultural  College,  Mississippi. 


Geological  Survey  of  Mississippi. 


BULLETIN 


A PRELIMINARY 


ON  SOME  OF 


CLAYS  OF  MI 


BY 


NO.  3. 


REPORT 


SSISSI  PPI 


W.  N.  LOGAN,  Geologist,  and  W.  F.  HAND,  Chemist. 


Fig.  1. — A Geological  Map  of  Mississippi. 


Geological  Survey  of  Mississippi 


BULLETIN  NO.  3. 


A PRELIMINARY  REPORT 


ON  SOME  OF  THE 


CLAYS  OF  MISSISSIPPI. 


GEOLOGICAL  CORPS. 


W.  N.  LOGAN 

W.  F.  HAND... 

J.  P.  MONTGOMERY. 

I.  D.  SESSUMS 

H.  S.  CHILTON 

G.  W.  HOLMES 

W.  STARK 


Geologist. 

Chemist. 

Assistant  Chemist. 
Assistant  Chemist. 
.Assistant  Chemist. 
.Assistant  Chemist. 
.Assistant  Chemist. 


Digitized  by  the  Internet  Archive 
in  2017  with  funding  from 

University  of  Illinois  Urbana-Champaign  Alternates 


https://archive.org/details/preliminaryreporOOIoga 


INTRODUCTION. 


One  of  the  most  valuable  natural  resources  of  Mississippi  is  an 
inexhaustible  supply  of  fine  clays.  Much  of  our  future  wealth  and 
industrial  progress  will  depend  upon  the  rapidity  with  which  this  re- 
source is  developed.  For  we  are  almost  wholly  dependent  upon 
clay  products  for  our  building  materials.  At  the  present  time  the 
clay  industry  of  the  State  is  in  its  infancy.  According  to  the  report 
on  the  mineral  resources  of  the  United  States  for  the  year  1903  we 
rank  thirtieth  in  the  list  of  clay  producing  states  in  value  of  clay  prod- 
ucts. The  total  value  of  the  clay  products  of  the  State  for  that  year 
was  $677,032.  This  amount  was  distributed  as  follows:  Brick, 
$658,491;  draintile,  $2,620;  red  earthenware,  $580;  stoneware,  $13,715. 

In  point  of  pottery  products,  with  only  two  steam  potteries  hav- 
ing, in  1903,  an  output  valued  at  $13,715  we  stand  in  sharp  contrast 
with  another  State  which  has  fifty  steam  potteries  and  an  out  put 
valued  at  six  million  dollars.  The  difference  is  not  due,  we  believe, 
to  any  deficiency  of  the  raw  material  and  in  that  fact  lies  the  hope 
and  the  promise  of  the  future.  For  with  available  beds  of  clay  that 
are  almost  inexhaustible  and  with  varieties  adapted  to  practically  all 
phases  of  the  ceramic  industry  there  is  every  hope  that  there  will  be 
a rapid  development  of  this  industry  in  Mississippi. 

The  following  report  is  preliminary  and  is  not  intended  to  be  com- 
plete. There  is  yet  much  important  work  to  be  done  in  the  investi- 
gation of  the  clays  mentioned  in  this  report.  Especially  is  this  true 
in  the  investigation  of  the  degree  of  refractoriness  of  some  of  the  clays. 
The  report,  however,  embodies  our  present  knowledge  of  the  quantity, 
distribution,  chemical  and  physical  properties  of  these  clays. 

THE  ORIGIN  AND  PROPERTIES  OF  CLAY. 

Definition. — Clay  is  a soft  rock  which  is  commonly  composed 
of  the  minerals,  kaolinite  and  quartz.  If  the  quartz  is  absent  the 
term,  kaolin,  or  pure  clay  is  applied  to  the  rock.  Of  kaolin  or  pure 
clay,  quartz  is  considered  an  impurity  but  not  of  clay  as  the  term 
is  ordinarity  used  unless  the  percentage  of  quartz  ranges  very  high 
in  which  case  the  clay  is  referred  to  as  an  impure  or  sandy  clay. 

Kaolin  is  a mixture  of  several  hydrous  or  anhydrous  silicates  of 
aluminum.  The  most  important  of  these  silicates  is  kaolinite,  a 
mineral  composed  of  alumina,  silica  and  water. 


6 


CLAYS  OF  MISSISSIPPI 


Impurities. — The  more  common  chemical  impurities  of  clay- 
are:  Iron  oxide,  iron  sulphate,  iron  sulphide,  iron  carbonate,  calcium 
carbonate,  magnesium  carbonate,  titanic  acid  and  carbon. 

The  chief  mineral  impurities  found  in  clay  are:  Quartz,  calcite, 
hematite,  limonite,  siderite,  feldspar,  mica,  pyrite,  rutile,  lignite  and 
dolomite. 

The  kind  and  quantity  of  the  impurities  affect  greatly  the  use- 
fulness of  the  clay.  The  presence  of  such  impurities  as  the  alkalies 
may  lower  the  fusion  point  of  the  clay  to  such  a degree  as  to  render 
it  unserviceable  for  even  the  ordinary  purposes  of  clay  manufacture. 
For  instance,  in  the  manufacture  of  brick  from  the  surface  loam  clay 
of  the  State  nodules  or  concretionary  masses  of  iron  and  lime  are 
brought  together  and  a flux  formed  which  melts  even  the  most  refractory 
sand  grains  and  causes  the  brick  to  run  together  in  a slaggy  mass. 
However  not  all  of  the  impurities  in  clay  are  detrimental  to  refrac- 
toriness. These  are  called  the  non-fluxing  impurities  while  the  former 
are  the  fluxing  impurities.  The  common  fluxing  impurities  are,  iron, 
lime,  magnesia,  and  potassa  compounds.  The  non-fluxing  impurities 
are  quartz,  titanic  acid,  water  and  organic  matter.  Under  certain 
conditions  referred  to  later  quartz  and  titanic  acid  lower  the  fusion 
point. 

Origin  of  Clay. 

Clay  results  from  the  decomposition  of  feldspathic  rocks.  Feld- 
spar is  one  of  the  principal  constituents  of  granite  and  other  igneous 
or  metamorphic  rocks  of  the  granitoid  group.  The  most  common 
source  of  clay  is  from  the  decomposition  of  the  feldspar,  orthoclase 
which  is  a potassium  aluminium  silicate.  In  the  disintegration  and 
decomposition  of  the  granite  the  potassium  of  the  feldspar  is  leached 
out  and  the  residual  aluminium  silicate  becomes  hydrated  forming  the 
minerals  kaolinite  and  its  associates.  These  form  the  basis  of  all 
clays.  Beds  of  these  minerals  are  kaolin  or  pure  clay  deposits.  But 
as  granite  contains  quartz,  mica  hornblende  and  smaller  amounts  of 
other  minerals  kaolin  beds  contain  more  or  less  of  these  substances 
as  impurities.  Especially  is  this  true  of  beds  which  have  not  been 
deposited.  But  as  these  substances  differ  in  size  of  grain  and  density 
they  may  be  separated  by  the  sorting  action  of  water  into  purer  beds 
of  kaolin  and  sand. 

Practically  all  of  the  clays  of  Mississippi  have  been  transported 
and  deposited  in  water.  Varying  conditions  of  transportation  and 
deposition  have  produced  varying  degrees  of  purity  in  the  clays.  Some 
of  the  clays  have  been  transported  from  far  beyond  the  northern  limits 


MISSISSIPPI  A.  & M.  COLLEGE 


7 


of  the  State  and  in  this  journey  toward  the  southern  border  have  been 
deposited  many  times.  To  some,  impurities  have  been  added,  from 
others,  extracted. 

The  principal  agents  in  the  transportation  of  clays  are  wind, 
water  and  ice.  The  wind  transported  clays  of  Mississippi  are  the 
clays  of  the  Loess  and  the  more  superficial  soil  clays;  though  it  is  pos- 
sible that  all  of  the  clays  of  the  state  are  to  a limited  extent  wind 
transported.  Many  of  the  clays  have  been  transported  by  sea  waves 
and  nearly  all  have  at  some  time  been  carried  by  streams. 

The  wind  transported  clays  are  land  derived  and  largely  land 
deposited.  The  water  transported  clays  were  deposited,  a few  in  deep 
sea  water,  more  in  shallow  shore  water  and  some  along  the  courses 
of  the  streams. 

The  transported  clay  may  have  various  intermediate  sources 
though  its  ultimate  source  is  always  the  decay  of  feldspathic  rocks. 
The  transported  clay  may  be  derived  from  these  decomposition  prod- 
ucts or  it  may  be  derived  from  previously  transported  beds  of  clay 
occurring  along  the  courses  of  streams  or  the  shore  of  the  sea. 

The  variation  in  the  purity  of  the  clay  or  the  sudden  changes  from 
clay  to  sand  may  be  due  to  a number  of  causes.  It  may  be  due  to  the 
variation  in  the  volume  of  water  in  the  transporting  stream  or  to  a 
variation  in  the  velocity  of  the  water,  to  a change  in  the  character  of 
the  rocks  which  the  streams  are  eroding  or  to  a change  in  the  position 
or  velocity  of  the  sea  currents. 

The  decomposition  products  of  igneous  rocks  form  the  larger 
part  of  the  material  of  clastic  or  fragmental  rocks.  Since  the  rocks  of 
our  State  belong  to  the  latter  class  clay  is  an  important  constituent 
of  nearly  all  Mississippi  rocks  and  soils.  But  while  clay  has  an  almost 
universal  distribution  the  conditions  under  which  kaolin  can  be  depos- 
ited are  so  rarely  fulfilled  that  such  deposits  are  few  in  number  and 
limited  in  area. 


The  Chemical  Properties  of  Clay. 

The  chemical  elements  usually  present  in  clay  are:  Oxygen,  sil- 
icon, aluminum,  iron,  calcium,  magnesium,  sodium,  potassium,  titanium, 
hydrogen,  carbon  and  sulphur.  The  last  two  may  occur  as  simple 
elementary  substances  uncombined.  The  other  elements  are  com- 
bined to  form  such  compounds  as  lime,  water  and  silica.  As  deter- 
mined by  chemical  analysis  these  elements  are  represented  as  combined 
with  oxygen  to  form  oxides. 


8 


CLAYS  OF  MISSISSIPPI 


TABLE  OF  CHEMICAL  COMPOUNDS  IN  CLAY. 


NAME  OF  COMPOUND. 

Silica  

Alumina  - 

"]  Ferric  oxide 

Fluxing  | Lime 

Im-  ^ Magnesia  

purities  | Potash  "]  alkalies 
j Soda  J 

Titanic  acid  

Sulphur  trioxide  

Carbon  dioxide  

Water 


CHEMICAL  SYMBOL. 

Si02 
AL  03 
Fe2  03 
CaO 
MgO 
K2  O 
I Na2  O 
Ti02 


C02 

h2  o 


In  the  clay  the  lime  is  usually  combined  with  carbon  dioxide  to 
form  calcium  carbonate  (CaC03 1 or  with  water  and  sulphur  trioxide 
to  form  hydrous  sulphate  of  lime  or  gypsum.  Other  combinations 
also  exist  so  that  an  ultimate  chemical  analysis  such  as  the  above  does 
not  present  the  amount  of  gypsum  for  instance  that  is  in  the  clay  but 
merely  the  amount  of  water,  calcium  and  sulphur  trioxide  which  it 
contains.  The  determination  of  the  percentage  of  the  different  mineral 
compounds  in  a clay  is  called  its  rational  analysis.  This  may  be  com- 
puted from  the  ultimate  analysis  and  is  useful  in  making  clay  mixtures. 


THE  PHYSICAL  PROPERTIES  OF  CLAY. 

Plasticity. 

A clay  is  plastic  when  it  can  be  easily  fashioned  by  the  hands 
into  a desired  form  and  has  the  property  of  retaining  that  form  when 
so  fashioned.  Dry  clay  of  any  kind  is  devoid  of  plasticity.  In  order 
that  a dry  clay  may  become  plastic  it  must  be  mixed  with  a certain 
amount  of  water.  The  amount  of  water  necessary  varies  with  the 
physical  condition  of  the  clay.  All  clays  do  not  become  plastic  when 
mixed  with  water.  This  fact  leads  to  the  conclusion  that  some  clays 
possess  an  inherent  property  or  properties  which  renders  them  plastic 
when  mixed  with  a certain  proportion  of  water.  Experience  demon- 
strates that  the  plasticity  of  a clay  is  not  due  to  a single  condition  but 
that  it  results  from  the  combined  action  of  a group  of  factors.  Some 
of  these  factors  are  well  known,  such  for  instance  as  the  presence  of 
uncombined  water.  There  are  other  factors  of  the  nature  of  which 
little  is  known. 

The  factors  which  seem  to  have  the  greatest  influence  upon  the 
plasticity  of  clay  are: 

1.  Fineness  of  Grain. — Some  clays  which  are  non-plastic  as 
taken  from  the  pit,  slacked  and  mixed  with  water  may  be  made  plastic 


MISSISSIPPI  A.  & M.  COLLEGE 


9 


by  reduction  to  minute  particles  before  being  mixed  with  water.  In 
like  manner  the  degree  of  plasticity  of  all  clays  may  be  increased. 
Fineness  of  grain  is  not  the  only  essential  factor,  however.  Some 
non-plastic  clays  are  of  very  fine  grain.  Some  substances  when  re- 
duced to  great  fineness  of  grain  remain  non-plastic  when  mixed  with 
water. 

2.  The  Presence  of  Uncombined  Water. — As  has  been  stated 
above  a dry  clay  is  not  at  all  plastic  but  it  may  become  highly  plastic 
when  mixed  with  a certain  amount  of  water.  The  water  acts  as  a 
lubricant  between  the  clay  particles  and  thereby  permits  greater  free- 
dom of  movement.  At  the  same  time  the  surface  tension  of  the  water 
holds  the  particles  and  permits  a movement  of  the  clay  particles  without 
interrupting  the  continuity  of  the  clay  mass.  An  effect  to  be  compared 
to  the  stretch  of  a rubber. 

3.  The  Presence  of  Combined  Water,  Bacteria  or  Some 
Substance  or  Condition  Which  May  be  Destroyed  by  Calcining.— 
When  a plastic  clay  has  been  subjected  to  a temperature  sufficient 
to  drive  off  its  combined  water  it  is  rendered  non-plastic.  Nor  can  its 
plasticity  be  restored  by  reducing  it  to  fine  powder  and  mixing  it  with 
water.  This  fact  proves  that  some  important  factor  of  plasticity  has 
been  destroyed  by  heating  the  clay.  It  has  been  found  by  practical 
tests  that  the  plasticity  of  a clay  is  increased  by  “ageing,”  “mellowing,” 
or  “curing”  the  clay.  These  are  terms  applied  to  the  same  process  which 
consists  in  storing  the  clay  for  a period  of  time  in  a damp  cool  place. 
For  instance  clay  which  has  been  stored  for  a time  in  a damp  cellar 
is  found  to  have  an  increased  plasticity.  This  increase  is  thought  to 
be  due  to  the  action  of  bacteria  working  in  the  clay.  It  is  found  also 
that  the  placticity  of  a clay  may  be  increased  by  the  addition  of  tannin 
or  the  addition  of  an  emulsion  of  straw. 

4.  The  Presence  of  Flat  and  Interlocking  Crystals.* — the 
presence  of  flat  crystals  aid  by  increasing  the  amount  of  surface  tension 
of  the  hydroscopic  moisture.  This  does  not  apply  to  the  large  macro- 
scopic plates  of  mica  which  sometimes  occur  in  clay  in  such  abundance 
as  to  be  detrimental  to  its  plasticity.  Crystals  which  are  curved  or 
have  angles  or  serrated  edges  present  interlocking  surfaces  which  in- 
crease the  tensile  strength  of  the  clay  and  may  also  increase  the  plas- 
ticity. 

A number  of  methods  of  determining  the  degree  of  plasticity  of 
a clay  have  been  suggested  but  none  of  them  are  entirely  satisfactory. 
The  old  method  of  determination  by  hand  moulding  is  still  the  most 
reliable. 

* See  Mo.  Geol.  Survey , Vol.  XI,  p.  101. 


10 


CLAYS  OF  MISSISSIPPI 


Fig.  2. — Briquettes  prepared  for  the  Tensile  Strength  Machine. 


Tensile  Strength. 

The  tensile  strength  of  the  clays  was  determined  by  the  use  of  a 
cement- testing  machine.  The  clays  were  first  ground  to  a fineness 
that  would  permit  them  to  pass  through  a seive  of  forty- 
mesh.  The  ground  clay  was  weighed  and  enough  water  added  to 
render  it  plastic,  a record  being  kept  of  the  amount  of  water  required 
for  each  clay.  When  the  clay  had  been  brought  to  the  desired  plas- 
ticity it  was  moulded  into  briquettes.  (See  Fig.  2.)  Brass  moulds 
were  placed  upon  an  oiled  glass  surface  and  the  clay  pressed 
into  them,  small  quantities  at  a time,  by  the  use  of  the  hand  and  a 
small  wooden  tamp  made  to  just  fit  the  mould.  The  upper  surface 
of  the  clay  was  cut  olf  and  smoothed  down  to  a level  with  the  upper 
surface  of  the  mould  by  the  use  of  a putty  knife.  Care  was  taken  to 
have  the  clay  well  pressed  against  the  surface  of  the  glass  so  as  to  insure 
as  smooth  a surface  for  the  under  side  of  the  briquette  as  the  upper. 
This  was  done  in  order  to  secure  uniform  conditions  in  drying,  as 
unequal  drying  of  opposite  surfaces  cause  the  briquettes  to  warp  and 
become  misshapen.  Care  was  taken  to  have  all  the  conditions  as 
uniform  as  possible  and  the  results  obtained  are  fairly  uniform  in  bri- 


MISSISSIPPI  A.  & M.  COLLEGE 


11 


quettes  of  the  same  clay.  The  wet  briquettes  were  weighed  and  then 
re-weighed  when  dry  in  order  to  ascertain  the  amount  of  water  lost  by 
evaporation  in  the  air.  Lines  one  inch  in  length  were  marked  on  the 
surface  of  the  briquettes  and  re-measured  when  dry  in  order  to  make 
an  estimate  of  the  shrinkage.  Before  breaking  the  briquettes  in  the 
testing  machine  the  air-shrinkage  was  calculated  and  taken  into  ac- 
count in  estimating  the  tensile  strength. 

The  clays  tested  exhibit  a great  range  in  tensile  strength.  The 
tough  gumbo-like  clays  of  the  Flatwoods  possess  the  maximum  tensile 
strength  while  the  non-plastic,  white,  highly  aluminous  clays  of  the 
Maben  type  possess  the  minimum. 

Shrinkage. 

The  amount  which  a clay  contracts  in  passing  from  a plastic  con- 
dition to  that  of  a solid  is  termed  its  shrinkage.  The  water  which  is 
added  to  the  clay  in  order  to  render  it  plastic  is  lost  by  evaporation, 
thereby  causing  a loss  of  volume.  The  loss  of  volume  or  shrinkage 
varies  greatly  in  different  clays  and  with  different  conditions  in  the 
same  clay.  Water  added  in  excess  of  the  amount  required  for  plastic- 
ity will  cause  a greater  loss  of  volume,  as  will  also  the  presence  of  air 
in  the  interstices  of  the  clay.  Considerable  water  may  exist  in  the  clay 
without  increasing  the  volume  but  whenever  the  particles  of  the  clay 
are  completely  enveloped  in  water  the  volume  and  the  plasticity  will 
be  increased. 

Water  absorbed  by  a clay  exists  either  interstitial  or  inter-par- 
ticle, i.  e.,  not  occupying  the  interstices  but  causing  a separation  of 
the  particles.  It  is  the  latter  which  increases  the  volume  of  a clay. 
Clays  of  coarse  grain  have  large  interstices  and  contain  large  quantities 
of  interstitial  water  but  less  inter-particle  water  than  clays  of  finer 
grain;  therefore  the  latter  shrink  more  than  the  former. 

Air-Shrinkage. — The  amount  of  contraction  which  a clay  under- 
goes when  drying  in  the  air  is  called  its  air-shrinkage.  The  amount  of 
air-shrinkage  depends  mainly  upon  two  factors:  The  amount  of  water 
absorbed  and  the  size  of  the  grain.  The  Mississippi  clays  examined 
exhibit  an  air-shrinkage  ranging  from  two  to  eleven  per  cent.  The 
amount  of  water  necessary  to  render  these  clays  plastic  varied  from 
sixteen  to  thirty-five  per  cent.  The  air-shrinkage  was  measured  on 
the  briquettes.  Lines  one  inch  in  length  were  made  on  the  surface 
of  the  briquettes  when  they  were  moulded  and  these  lines  re-measured 


12 


CLAYS  OF  MISSISSIPPI 


when  the  briquettes  had  dried.  The  difference  expressed  the  amount 
of  air-shrinkage. 

The  maximum  air-shrinkage  was  attained  by  the  gumbo  clay 
belonging  to  the  Flatwoods-Eocene.  Samples  taken  from  Winston 
and  Oktibbeha  counties  gave  an  average  shrinkage  of  eleven  per  cent. 
This  clay  contains  a great  quantity  of  silica  in  a very  finely  divided 
state.  A clay  which  contains  a still  greater  quantity  of  silica  is  the 
fire  clay  from  Holly  Springs,  yet  this  clay  has  an  air-shrinkage  of  only 
two  per  cent.  The  silica  in  the  last  named  clay  is  in  large  particles, 
many  of  the  particles  exceeding  in  size  a grain  of  mustard.  The  action 
of  these  two  clays  illustrates  clearly  the  effect  of  size  of  grain  upon  the 
air-shrinkage. 

Fire-Shrinkage. — The  fire-shrinkage  is  the  further  contraction 
which  an  air- dried  clay  undergoes  in  being  heated  to  the  point  of 
vitrification.  The  amount  of  such  contraction  varies  with  the  conditions 
of  the  clay.  It  is  dependent  upon  the  amount  of  organic  matter,  the 
amount  of  lime  and  the  amount  of  combined  water  in  the  clay. 

Other  Effects  of  Drying. — Some  clays  lose  their  water  more 
rapidly  than  others.  Coarse-grained  clays  dry  more  rapidly  than  fine- 
grained clays  because  the  capillary  tubes  formed  by  the  particles  of 
the  clay  are  larger  and  more  regular  in  the  former  and  the  water  is 
conveyed  more  rapidly  to  the  surface.  The  tubes  formed  by  the  minute, 
particles  of  a fine-grained  clay  are  exceedingly  small  and  irregular, 
consequently  the  movement  of  the  water  is  greatly  retarded.  Rapid 
drying  of  a fine-grained  clay  tends  to  cause  cracks,  for  the  reason 
that  there  is  an  unequal  contraction.  The  outside  of  the  clay  losing 
its  moisture  more  rapidly  than  the  inside,  shrinks  more  rapidly  and 
hence  pulls  apart. 

Speed  of  drying  is  an  important  factor  in  the  economy  of  the 
clay  industry.  Before  any  clay  can  be  burned  it  is  necessary  that  it 
first  be  dried.  Clays  which  dry  rapidly  without  cracking  or  checking 
are  of  much  greater  value  from  an  economic  standpoint  than  slow- 
drying  clays.  The  former  can  be  dried  by  artificial  driers  employing 
varying  temperatures,  in  a short  period  of  time.  The  latter  must  be 
dried  slowly  under  uniform  conditions  of  temperature.  Slow  drying 
clays  are  tempered  in  some  instances  in  order  to  reduce  their  shrinkage 
and  increase  the  rapidity  of  their  drying.  To  accomplish  this  they 
may  be  mixed  with  a coarse  clay,  with  sand  or  with  crushed  brick  or 
stoneware. 


MISSISSIPPI  A.  & M.  COLLEGE 


13 


Fig.  3. — Electric  Oven  for  Testing  Fusibility  of  Clays. 

Fusibility. 

Three  stages  are  usually  recognized  in  the  fusion  of  a clay,  namely: 
Incipient  fusion,  vitrification  and  viscosity.  In  the  first  stage  the  more 
fusible  particles  become  soft  and  upon  cooling  cement  together  the 
more  refractory  particles  forming  a hard  mass.  In  the  second  stage  the 
clay  particles  become  soft  enough  to  close  up  all  af  the  pore  spaces  so 
that  further  shrinkage  of  the  clay  is  impossible.  When  the  mass 
becomes  cool  it  forms  a dense  solid  body  which  is  glassy  on  a fractured 
surface.  In  the  third  stage  the  clay  body  becomes  so  soft  as  to  no  longer 
retain  its  shape  and  flows. 

The  fusibility  of  a clay  depends  upon  a number  of  factors,  but 
the  most  important  ones  are  the  amount  and  kind  of  fluxing  impurities 
in  the  clay  and  the  fineness  of  the  grain. 

For  the  determination  of  the  fusibility  of  clays  Seger  cones  are 
ordinarily  used.  These  cones  are  made  of  a mixture  of  substances  of 
known  fusibility.  They  are  arranged  in  a series  representing  fusion 
points  from  590°C  (1,094  °F)  to  1,850°C  (3,362°F).  These  cones, 

together  with  the  clay  to  be  tested  are  placed  in  a furnace  or  oven  and 
the  heat  applied.  The  cone  which  loses  its  shape  at  the  moment  that 
the  clay  does  determines  the  fusion  point  of  the  clay. 

Pyrometers  of  various  kinds  are  also  used  for  determining  the 
* temperatures  of  kilns  and  furnaces  and  the  fusion  points  of  different 
substances.  One  of  these  is  the  thermo-electric  pyrometer.  It  con- 
sists of  a thermo-electric  couple  which  generates  an  electric  current 
when  heated,  the  intensity  of  the  current  increasing  with  the  tempera- 
ture. The  current  is  measured  by  means  of  a galvanometer.  The 
thermopile  consists  of  a platinum  wire  and  a wire  composed  of  90  per 


14 


CLAYS  OF  MISSISSIPPI 


ent.  platinum  and  10  per  cent,  rhodium.  These  wires,  protected 
by  clay  tubes,  are  inserted  into  the  furnace  usually  through  a small 
opening  in  the  door. 

Hardness. — The  hardness  of  clays  ranges  in  the  different  varieties 
from  1 to  3.  The  maximum  degree  of  hardness  is  reached  in  the  flint 
clays  while  the  minimum  is  represented  by  the  chalk-like  beds  of 
kaolin.  Burnt  clay  has  a much  higher  degree  of  hardness  than  the  raw 
clay.  Vitrified  brick  and  some  other  clay  products  reach  a hardness 
equal  to  that  of  quartz  and  will  readily  scratch  glass. 

Color. — The  color  of  clays  is  an  exceedingly  variable  property. 
Many  tints  and  shades  are  represented.  White  clays  are  usually 
devoid  of  coloring  matter.  But  some  white  clays  contain  enough  iron 
to  produce  a darker  shade  when  burned  in  an  oxidizing  flame.  Or 
the  presence  of  titanium  may  produce  a purple  tint  when  the  clay  is 
burned  at  a high  temperature.  The  color  of  a clay  may  be  due  to  the 
presence  of  organic  matter  or  to  the  presence  or  some  iron  or  manganese 
compound.  The  color  of  a clay  may  be  greatly  changed  by  burning. 
For  instance  a black  clay  whose  color  is  due  to  the  presence  of  organic 
matter  alone  may  burn  to  a white  shade.  A red  or  yellow  clay  often 
burns  black,  due  to  an  excess  of  iron. 

The  color  to  which  a clay  will  burn  often  has  an  important  bearing 
on  its  value.  A clay  which  is  of  value  as  a stoneware  clay  may  be 
entirely  worthless  as  a white  ware  clay  because  of  the  presence  of 
coloring  matter  which  would  be  developed  by  burning.  Even  in  com- 
mon brick  clays  the  color  is  of  importance.  The  nearly  colorless 
Milwaukee  brick  clay  is  of  greater  commercial  value  than  the  more 
common  red  or  yellow  burning  brick-clays.  The  only  thoruoghly 
reliable  test  to  determine  the  color  of  the  burnt  product  is  to  burn  the 
clay  under  the  same  conditions  which  the  product  is  to  be  subjected. 

Odor — Clays  containing  a large  amount  of  kaolin  have  what  is 
termed  an  argillaceous  of  clay-like  odor.  Some  clays  containing  de- 
caying organic  matter  have  a fetid  odor. 

Taste. — The  presence  of  certain  soluble  salts  as  common  salt, 
alum,  ferrous  sulphate,  etc.,  may  be  detected  by  tasting  the  clay. 
Clay-workers  often  employ  this  method  for  determining  the  amount 
of  clay  substance  and  the  plasticity  of  the  clay.  The  clay  is  crushed 
between  the  teeth  and  mixed  with  the  saliva  in  order  to  determine 
the  amount  of  grit  and  the  readiness  with  which  it  may  be  moulded. 

Feel. — Some  clays  are  harsh  to  the  touch.  Others  are  smooth. 
Some  may  have  an  unctious  feel  like  talc  and  still  be  non-plastic  though 
most  unctious  clays  are  plastic.  As  a rule  a harsh  clay  is  impure  while 


MISSISSIPPI  A.  & M.  COLLEGE 


15 


an  unctious  clay  contains  a large  amount  of  clay-b:»su.  But  some  clays 
containing  a large  amount  of  sandy  matter  may  be  smooth  to  the  feel 
because  of  the  fineness  of  the  grain. 

Slacking. — When  air-dried  clay  is  placed  into  water  it  breaks 
up  into  small  fragments.  This  process  of  disintegration  is  termed, 
“slacking,’’  The  size  of  the  fragments  or  grains  are  fairly  uniform 
for  the  same  clay  but  vary  greatly  in  different  clays.  They  also  vary 
in  shape.  Some  are  flat,  some  cuboidal,  others  irregular.  As  the 
fragments  separate  they  absorb  water  and  increase  in  size.  Slacking 
takes  place  wherever  an  air-dried  clay  surface  is  exposed  to  the  action 
of  water. 

The  speed  of  slacking  varies  in  different  clays.  Clays  of  marked 
density  such  as  shale  and  flint  clays  disintegrate  slowly  while  the  lighter 
brick  and  stoneware  clays  rapidly  fall  to  pieces.  Of  the  Mississippi 
clays,  the  Tishomingo  shale  and  the  Flatwood’s  clay  have  the  least 
slacking  speed  while  the  white  clay  from  Tishomingo  county,  the 
Brunner  fire  clay,  the  Grenada  brick  clay  and  many  of  the  pottery 
clays  all  slack  very  rapidly.  A clay  which  is  used  for  any  purpose 
requiring  moulding  and  without  grinding  should  have  at  least  a mod- 
erate slacking  speed.  A clay  having  a poor  slacking  speed  causes  loss 
of  time  when  mixed  either  in  the  wet  pan  or  the  pug  mill. 

Structure. — The  structure  of  a clay  refers  to  its  mode  of  occur- 
rence in  the  out-crop  or  pit.  It  may  have  a lamellar  structure,  occur- 
ring in  thin  plates  or  beds  of  varying  composition  or  color.  It  may  be 
massive,  having  no  stratification.  Sometimes  both  varieties  occur 
in  the  same  pit.  Either  massive  or  lamellar  clay  may  be  joined,  i. 
e.,  separated  in  blocks  by  crevices.  Either  may  have  a conchoidal 
fracture  though  such  structure  is  more  common  in  the  massive  clays. 

Specific  Gravity. — The  specific  gravity  of  clays  varies  usually 
from  1.50  to  2.50,  but  there  are  some  which  fall  below  or  exceed  these 
limits.  Pure  kaolin,  or  pure  sand,  has  an  average  specific  gravity  not 
far  from  2.63.  So  that  mixtures  of  these  substances  in  varying  propor- 
tions does  not  alter  the  specific  gravity  greatly.  The  presence  of  such 
impurities  as  the  iron  compounds  may  greatly  increase  the  specific 
gravity  of  the  clay.  Methods  of  determining  specific  gravity  vary 
and  give  different  results  for  the  same  clay.  By  using  the  pycnometer 
the  specific  gravity  of  the  individual  grains  is  obtained  and  taken  as  the 
specific  gravity  of  the  clay.  Another  method  is  to  determine  the  specific 
gravity  of  lumps  of  clay  coated  with  parafin,  thus  considering  the  pore 
spaces  a part  of  the  clay  mass.  The  results  are  less  in  the  latter  case. 


16 


CLAYS  OF  MISSISSIPPI 


Classification  of  Clays. 

Clays  are  usually  classified  either  according  to  their  properties 
or  their  uses.  Under  either  method  a great  many  systems  of  classifi- 
cation are  possible.  As  regards  their  properties  clays  may  be  classi- 
fied: 

1.  According  to  their  chemical  composition,  as  silicious,  aluminous, 
calcareous,  ferruginous,  etc.,  clays. 

2.  According  to  their  mineral  constituents,  as  micaceous,  quartzitic, 
saliferous,  gypsiferous,  etc.,  clays. 

3.  According  to  texture,  as  coarse,  fine,  etc.,  clays. 

4.  According  to  color,  as  white,  gray,  etc.,  clays. 

5.  According  to  odor,  as  fetid,  argillaceous,  etc.,  clays. 

6.  According  to  taste,  as  saline,  acrid,  etc.,  clays. 

7.  According  to  plasticity,  as  plastic  or  non  plastic  clays. 

8.  According  to  feel,  as  unctuous,  gritty,  etc.,  clays. 

9.  According  to  chemical  reaction,  as  acid  or  alkaline  clays. 

10.  According  to  action  under  high  temperatures,  as  fusible  or  re- 
fractory clays. 

Clays  may  also  be  classified  according  to  their  origin  as  residual 
or  transported  clays. 

The  uses  of  clays  are  so  many  and  varied  that  it  is  difficult  to 
make  a short  comprehensive  classification  based  upon  that  factor. 
Some  of  the  principal  uses  of  clays  are  given  in  the  following  grouping: 

1.  Brick  Clays. — a.  Common  brick. — These  may  be  classified 
according  to  the  method  of  moulding  as  soft-mud,  stiff  -mud,  or  dry- 
pressed;  according  to  color  as  red,  salmon,  mottled,  etc.;  according  to 
position  in  the  kiln  as  eye,  body,  etc. ; according  to  position  in  the  build- 
ing as  front,  back,  etc.;  according  to  form  as  hollow,  ornamental,  etc.; 
according  to  treatment  in  burning  as  vitrified,  lithified,  glazed,  enamelled 
or  adobe  (sun-dried). 

b.  Vitrified  brick —Brick  made  of  clay  shales  and  used  for  pave- 
ments and  buildings.  They  are  a compact,  non-porous,  stoney  brick 
having  great  crushing  strength  and  a high  degree  of  hardness. 

c.  Fire  Brick. — Brick  made  from  highly  refractory  clays  and  used 
in  the  manufacture  of  ovens,  furnaces,  as  linings  for  fire  places,  fire  boxes 
and  stoves. 

2.  Tile  Clay. — May  be  either  common  clay,  shale,  or  fire  clay 
used  in  the  manufacture  of  drain  tile,  soil  tile,  irrigating  tile,  roofing 
tile,  floor  tile,  wall  tile  and  fire  place  tile. 


MISSISSIPPI  A.  & M.  COLLEGE  17 

3.  Flue  Clay. — Clay  which  is  used  in  the  manufacture  of  chim- 
ney flues,  ventilating  flues,  and  flue  brick  and  tile. 

4.  Stoneware  Clay. — Used  in  the  manufacture  of  jugs,  churns, 
crocks,  pitchers,  jars,  urns,  jardiniers,  and  sewer-pipe. 

5.  Earthenware  Clay —Employed  in  the  manufacture  of  un- 
glazed ware,  such  as  flower  pots,  filters  and  drain  tile. 

6.  China  Clay. — Used  in  the  production  of  chinaware,  porcelain, 
granite  ware,  white  ware,  such  as  urinals,  water  closet  bowls,  basins, 
lavatories  and  sinks. 

7.  Cement  Clay. — Used  in  the  manufacture  of  Portland  cement. 
When  employed  for  this  purpose  the  clay  is  mixed  with  a certain 
proportion  of  limestone.  After  being  pulverized  it  is  burned  to  a cinder 
and  reground. 

8.  Ballast  Clay. — Employed  in  the  manufacture  of  road 
ballast  for  walks,  wagon  roads,  railroads,  for  barn  floors  and  also 
for  the  purpose  of  deadening  floors. 

9.  Paper  Clay. — Used  as  a filler  for  printing  paper,  wall  paper, 
etc.  The  clay  for  this  purpose  is  utilized  in  the  raw  state. 

10.  Fuller’s  Earth  Clay. — Is  used  to  refine  crude  oil,  either 
vegetable  or  mineral.  Most  clays  used  for  this  purpose  require  wash- 
ing. All  clay  must  be  thoroughly  dried  and  pulverized. 

11.  Adulterant  Clays. — These  are  employed  in  the  adultera- 
tion of  soap,  paint  or  food. 

12.  Terra  Cotta  Clay. — Used  in  the  manufacture  of  terra 
cotta  brick  and  lumber,  both  plain  and  ornamental. 

13.  MiscellaneousUses  of  Clay. — In  the  manufacture  of  chem- 
ical apparatus,  such  as  evaporating  dishes,  pestles,  mortars,  ovens, 
crucibles,  etc.;  puddling  in  reservoirs;  to  temper  soil;  as  an  absorbent; 
for  medicinal  purposes;  for  artists’  moulding  material;  in  relief  mod- 
elling in  schools;  in  gas  retorts;  glass  pots,  smelters,  saggars,  electric 
insulating  tubes,  blocks,  etc. 

Stoneware  Clays. 

The  stone  ware  clays  of  Mississippi  now  in  use  compare  very 
favorably  with  those  being  used  in  other  States,  as  regards  the  chem- 
ical and  physical  properties  of  the  clays,  and  the  quality  of  the  pro- 
duct. The  greater  number  of  potteries  of  the  State  are  small  hand 
potteries  and  the  clay  is  used  as  it  comes  from  the  pit  except  that  it 
is  stirred  for  a short  time  in  a small  mixer.  The  kilns  or  ovens  used 
are  small  oblong  up-draught  ovens  of  a few  hundreds  gallons  ca- 
pacity. The  turning  wheels  are  usually  of  a home-made  pattern 


18 


CLAYS  OF  MISSISSIPPI 


rotated  by  pushing  a lever  with  the  foot,  a process  called  “kicking.” 
The  clay  product  is  air-dried  before  being  burnec  The  glaze  is  de- 
veloped by  dipping  or  spraying  the  vessel  with  a “slip”  clay  solution. 
The  slip  clay  is  a clay  of  low  fusibility  imported  from  New  York. 
The  glaze  is  developed  and  the  clay  burned  or  lithified  at  one  operation. 

In  nearly  every  instance  the  quality  of  the  ware  might  be  improved 
by  the  employment  of  better  methods,  machinery  and  kilns.  A 
fact  which  is  apparent  wherever  the  product  from  the  small  pottery 
is  brought  in  competition  with  that  from  the  larger  and  better  equipped 
steam  pottery.  Washing  the  clay  is  ordinarily  considered  too  ex- 
pensive a process  to  be  used  in  the  manufacture  of  stoneware,  but 
it  would  greatly  enhance  the  value  of  some  clays,  and  especially 
those  destined  for  use  in  the  manufacture  of  decorated  ware.  The 
use  of  the  wet  pan  or  chaser  instead  of  the  mixer  in  common  use  would 
add  to  the  quality  of  the  product. 

Essential  Qualities. — A good  stoneware  clay  should  be  plastic 
when  mixed  with  water  so  that  it  may  be  easily  fashioned  by  the 
hands.  The  quantity  of  iron  in  the  clay  should  be  small.  But  the 
per  centage  may  be  greater  in  case  the  brown  glaze  is  to  be  used.  In 
any  case  the  iron  should  be  well  pulverized  and  distributed  in  the  clay 
so  as  to  not  cause  dark  spots.  Stoneware  containing  iron  is  stronger 
as  a rule  than  stoneware  free  from  iron,  but  the  former  is  less  desirable 
to  the  trade  because  of  the  discoloration.  The  amount  of  iron  in 
stonewares  clays  may  vary  from  one  to  five  per  cent.  It  ranges  in  the 
Mississippi  stoneware  clays  now  in  use  from  1.05  to  4.14  per  cent. 
The  brown  glaze  is  used  with  the  latter.  It  would  doubtless  be 
necessary  to  remove  a part  of  the  iron  by  washing  before  a white  glaze 
could  be  developed. 

The  amount  of  alumina  in  the  Mississippi  clays  now  in  use  ranges 
from  14.46  to  27.79  per  cent.  The  minimum  amount  of  alumina 
for  such  ware  is  in  the  neighborhood  of  12  per  cent. 

The  amount  of  sandy  matter  or  uncombined  silica  in  these  clays 
varies  from  15.42  to  46.95  per  cent,  and  the  total  amount  of  silica 
from  58.05  to  73.40  per  cent.  Other  conditions  being  normal  the 
presence  of  uncombined  silica  is  not  detrimental  providing  the  par- 
ticles are  not  extremely  large  or  extremely  small  and  the  amount  does 
not  exceed  forty-five  per  cent.  The  presence  of  sandy  matter  is  an 
aid  to  rapid  drying  and  to  burning,  without  danger  of  checking  or 
cracking  the  ware.  It  also  decreases  the  shrinkage  and  gives  greater 
strength  to  the  product. 


MISSISSIPPI  A.  & M.  COLLEGE 


19 


A first  class  stoneware  clay  is  comparatively  free  from  such  fluxing 
impurities  as  calcium  carbonate,  caHum  sulphate,  magnesium  sulphate, 
etc.  Though  these  substances  are  not  detrimental  in  minute  quantities, 
they  produce  blisters  on  the  surface  and  flaws  in  the  body  of  the  ware 
when  present  in  excess  of  two  or  three  per  cent.  The  amount  of  lime 
in  the  Mississippi  clays  now  in  use  ranges  from  .32  to  2 per  cent,  and 
the  amount  of  magnesia  from  .25  to  .83  per  cent. 

Comparison  of  Stoneware  Clay. 

In  the  following  table  the  average  analysis  of  eight  stoneware 
clays  now  being  used  in  Mississippi  is  compared  with  the  average 
of  ten  Pennsylvania  stoneware  clays  *and  eight  similar  clays  from 
Missouri!. 

* See , “ Clays  and  Clay  Industries  of  Pa.”  Hopkins. 

* See,  Mo.  Geo  . Survey,  Vol.  XI,  Wheeler. 

PENNSYLVANIA.  MISSISSIPPI..  MISSOURI. 


Clay  Base  56.65  59.05  60.36 

Sandy  Matter 37.45  38.49  23.30 

Fluxing  Matter  4.44  3.45  7.79 

Moisture 1.57  1.50  8.52 

Total  Silica 65.00  64.23  59.84 


There  is  a very  slight  difference  in  the  results  obtained  from  the 
three  averages.  The  Mississippi  clays  have  a higher  clay  base  than 
the  Pennsylvania  clays  and  slightly  less  than  the  Missouri.  They 
have  less  total  silica  than  the  Pennsylvania  and  more  than  the  Missouri. 
But  they  have  less  fluxing  impurities  than  either  of  the  others.  They 
are  therefore  more  refractory  providing  the  silica  is  of  the  same  degree 
of  fineness. 

In  order  that  a comparison  may  be  made  between  clays  now  in 
use  in  Mississippi  and  those  not  in  use  but  available  I have  selected 
ten  of  the  latter  and  obtained  the  average  analysis.  This  analysis 
should  be  compared  with  those  in  the  table  above. 

MISSISSIPPI  CLAYS  NOT  IN  USE. 


Clay  Base  72.32 

Sandy  Matter 12.73 

Fluxing  Matter  3.07 

Moisture 1.49 

Total  Silica 56.01 


These  clays  contain  a much  higher  per  centage  of  clay  substance, 
and  a very  much  smaller  per  centage  of  silica,  sandy  matter  and  fluxing 
impurities.  Thev  are  therefore  more  refractory  under  similar  condi- 
tions of  grain.  The  low  per  centage  of  iron  makes  them  desirable 
clays  for  the  manufacture  of  white-glaze  ware. 


20 


CLAYS  OF  MISSISSIPPI 


Below  we  give  the  complete  average  analysis  of  these  ten  Mis- 
sissippi clays  not  in  use. 


Moisture __ 0.98 

Loss  on  Ignition  9.39 

Silica  56.01 

Ferric  Oxide 2.28 

Alumina  -...28.79 

Lime  0.50 

Magnesia  0.28 

Sulphur  Trioxide  0.20 


The  use  of  these1  clays  in  the  manufacture  of  the  various  grades 
of  ornamental  or  decorated  stoneware  has  been  tested  to  a limited 
extent  only.  But  the  experiments  already  made  have  been  so  success- 
ful as  to  leave  little  room  for  doubt  that  here  is  a profitable  field  for 
the  investor.  Both  the  physical  and  the  chemical  properties  of  these 
clays  prove  their  adaptibility  for  the  manufacture  of  such  ware  as 
the  Yellow,  the  Rockingham,  the  Rookwood,  and  the  Weller  ware. 
These  wares  differ  from  the  ordinary  stonewares  in  the  process  of 
burning  and  glazing.  In  the  manufacture  of  ordinary  stoneware 
the  burning  and  glazing  is  completed  in  one  operation.  That  is,  the 
air  dried  clay  vessels  are  dipped  in  the  glazing  solution  then  placed 
in  the  kiln.  The  glaze  clay  or  mixture  fuses  at  a lower  temperature  than 
the  body  of  the  ware  so  that  by  the  time  the  latter  is  lithified  the  former 
is  thoroughly  fused  forming  a smooth  hard  surface. 

In  the  manufacture  of  Yellow  ware  the  clay  vessel  is  first  placed 
into  a biscuit  kiln  and  lithified.  It  is  then  glazed  by  a second  burn- 
ing. The  latter  process  is  followed  in  the  manufacture  of  decorated 
ware  except  that  the  desired  coloring  matter  is  placed  on  the  ware 
before  the  glaze  mixture.  This  coloring  matter  is  usually  placed  on 
the  ware  by  means  of  a brush  in  the  hands  of  a skilled  decorator. 

White  Ware  Clays. 

In  the  manufacture  of  white  ware  such  as  porcelain  and  C.  C. 
ware  a mixture  of  clay,  quartz,  feldspar  and  kaolin  is  used.  The 
amount  of  each  one  of  these  substances  used  differs  with  the  grade 
of  ware  and  also  with  the  purity  of  the  substances.  The  amount  of 
quartz  and  feldspar  used  in  some  ware  is  a little  more  than  one-third 
each  of  the  total  amount  and  the  kaolin  and  clay  a little  less  than  one- 
sixth  (each)  of  the  total  amount. 

In  order  to  present  the  essential  chemical  properties  of  a white 
ware  clay  and  at  the  same  time  compare  some  of  the  Mississippi  clays 
with  clays  being  used  in  the  manufacture  of  white  ware  elsewhere, 


MISSISSIPPI  A.  & M.  COLLEGE  21 

the  following  is  given.  Three  of  the  clays  selected  are  from  Missis- 
sippi, three  from  other  states*  and  three  from  China*. 

* See , N.  J.  Geol.  Survey,  Cook,  1878;  and  Tables  of  Analyses  of  Clay,  Crossley, 
Ind.,  1889. 

*See  Brickmaker,  Vol.  XIII,  No.  3,  Chicago ; and  Crossley,  loc.  cit. 
COMPARISON  OF  WHITE  WARE  CLAY. 


Silica  (Si02  ) - 

MISSISSIPPI. 

51.71 

OTHER  U.  S.  CLAYS. 

53.34 

CHINA. 

52.67 

Alumina  (Ah  03  ) . 

32.51 

29.07 

32.68 

Ferric  Oxide  (Fe2  03  ) - 

2.30 

1.26 

1.64 

Lime  (CaO)  

0.45 

0.71 

0.33 

Magnesia  (MgO)  

0.34 

0.20 

0.58 

Alkalies  (K2  0,  Na2  0)  ... 

0.64 

1.77 

Volatile  Matter  

12.60 

14.81 

9.47 

One  of  the  clays  in  the  second  column  was  washed  before  being 
analyzed  and  doubtless  much  of  the  impurities  was  removed.  The 
three  Mississippi  clays  were  analyzed  as  taken  from  the  pit  without 
washing.  The  best  of  the  latter  contains  4.21  per  cent,  more  alumina 
than  the  average  and  1.34  per  cent,  less  iron  than  the  average.  It 
is  only  in  the  greater  per  centage  of  iron  that  the  average  of  the  Missis- 
sippi clays  is  inferior  to  the  other  average.  This  per  centage  of  iron 
however,  is  not  excessive  and  much  of  it  can  be  removed  by  wash- 
ing. These  clays  are  not  wanting  in  any  of  the  essential  physical 
properties  in  so  far  as  the  laboratory  tests  are  competent  to  determine. 

Clays  number  1,  3,  5 and  6 by  reason  of  their  physical  properties 
may  be  classed  with  the  best  of  the  three  Mississippi  clays  as  white 
ware  clays.  Many  of  the  pottery  clays,  by  washing,  would  be  rendered 
suitable  to  be  placed  in  this  class. 

Paper  Clays. 

In  the  manufacture  of  paper,  clay  is  being  used  as  a filler  for  the 
wood  or  straw  pulp.  It  gives  weight  and  smoothness  to  the  paper 
thereby  making  possible  a clearer  impression  in  writing  or  printing. 
Formerly  talc  and  whiting  were  used  exclusively  for  this  purpose 
but  since  the  preparation  of  these  substances  is  an  expensive  process 
the  use  of  clay  has  in  a measure  supplanted  them.  The  clays  are  used 
in  their  native  state.  The  essential  qualities  of  a paper  clay  are: 
Freedom  from  coloring  matter,  sandy  matter  or  grit;  fineness  of  grain; 
ease  in  slacking;  and  absence  of  substances  which  by  contact  with 
the  air  might  oxidize  and  discolor  the  paper. 

At  the  present  time  none  of  the  clays  of  Mississippi  are  being 
utilized  in  the  manufacture  of  paper,  though  they  compare  very  fa- 
vorably with  clays  being  used  for  that  purpose  in  other  states.  In 


22 


CLAYS  OF  MISSISSIPPI 


the  table  below  the  analysis  of  one  of  the  Mississippi  white  clays  is 
compared  with  the  analysis  of  a paper  clay  from  Georgia*. 

* See,  “Clays  of  Georgia ,”  Ladd,  1898. 


GEORGIA 

MISSISSIPPI 

CLAY. 

CLAY. 

Moisture  

0.99 

1.09 

Loss  on  Ignition  

12.98 

13.28 

Silica  

46.47 

47.40 

Alumina  

39.13 

36.72 

Ferric  oxide  

1.05 

0.96 

Lime 

0.40 

0.24 

Magnesia  

0.17 

0.19 

The  Mississippi  clay  contains  a fraction  more  silica  and  a little 
less  iron  and  alumina  than  the  Georgia  clay.  On  the  whole  it  is  as 
desirable  a clay.  Clays  number  60,  66  and  76  are  just  as  suitable 
for  paper  clays  as  the  above.  Many  of  our  white  pottery  clays  could 
be  rendered  suitable  for  this  industry  by  washing  them. 

Terra  Cotta  Clays. 

The  majority  of  terra  cotta  clays  now  in  use  require  washing 
in  order  to  secure  uniformity  of  color.  Clays  of  various  colors  are 
are  used  for  terra  cotta  brick  or  lumber,  but  it  is  very  desirable  that 
the  coloring  matter  be  uniformly  distributed  so  as  to  preclude  blotch- 
ing or  spotting  of  the  ware  in  burning.  Any  good  stoneware  clay 
of  uniform  color,  fair  degree  of  plasticity,  and  small  amount  of  shrink- 
age may  be  used  for  terra  cotta,  providing  it  will  dry  and  burn  readily 
without  checking  or  cracking.  Many  of  the  excellent  stoneware 
clays  mentioned  in  this  report  meet  these  requirements  and  some 
of  them  are  sufficiently  uniform  in  color  and  free  from  other  detri- 
mentals to  be  used  without  washing.  Under  proper  treatment  many 
of  these  clays  may  be  made  into  buff  or  cream  colored  terra  cotta 
products. 

The  manufacture  of  terra  cotta  is  an  industry  which  has  not  yet 
been  introduced  into  Mississippi.  But  because  of  the  lack  of  native 
building  stone  and  the  constantly  increasing  demand  for  structural 
clay  products  we  may  hope  that  the  day  is  not  far  distant  when  the 
manufacture  of  terra  cotta  will  form  no  small  part  of  our  industrial 
resources. 

Fire  Clays. 

A fire  clay  is  a highly  refractory  clay.  It  possesses  the  property 
of  retaining  its  shape  at  temperatures  which  would  be  sufficient  to 
fuse  common  clay.  Its  refractory  properties  makes  possible  its  use 
in  places  subjected  to  exceedingly  high  temperatures,  such  as  ovens, 


MISSISSIPPI  A.  & M.  COLLEGE 


23 


kilns,  furnaces,  crucibles,  glass  pots,  and  saggars.  Fire  clay  like  com- 
mon clay  varies  much  in  its  physical  and  chemical  properties.  Some 
fire  clays  are  very  plastic  others  are  non-plastic.  Some  contain  large 
quantities  of  free  silica  others  contain  no  free  silica.  And  yet  the  one 
may  be  as  refractory  as  the  other.  Then  again  of  two  clays  having 
the  same  amount  of  silica  the  one  may  be  refractory  and  the  other 
not;  for  the  reason  that  the  one  may  be  free  from  fluxing  impurities 
or  have  only  a moderate  amount  while  the  other  may  have  a high  per- 
centage of  fluxing  impurities.  Or  the  one  may  have  its  sandy  matter 
in  a coarsely  divided  state  while  the  sandy  matter  in  the  other  may 
be  finely  divided.  For  the  last  mentioned  reason  the  chemical  anal- 
ysis of  a clay  cannot  be  used  alone  as  a criterion  of  refractoriness. 
The  color  of  a clay  is  no  index  to  its  refractoriness  as  is  demonstrated 
by  the  great  variation  in  the  color  of  fire  clays.  The  fire  test  is  the 
most  satisfactory  one  for  estimating  degree  of  refractoriness.  Such 
tests  have  demonstrated  that  some  of  the  clays  mentioned  in  this 
report  are  refractor  to  a high  degree  and  merit  being  classed  as  fire 
clays.  In  order  that  we  may  form  some  conception  of  the  class  to 
which  these  fire  clays  belong  I have  taken  the  average  analysis  of  three, 
high  in  total  silica  content,  and  compared  it  with  the  average  analysis 
of  three  New  Jersey  fire  clays*  also  high  in  total  silica  content.  These 
clays  are  used  in  the  manufacture  of  fire  brick  and  are  selected  as  rep- 
resenting about  the  same  chemical  class  to  which  the  Mississippi  clays 
belong. 

*See,  N.  J.  S.  Geol.  Sur.  Report  on  Clays,  Cook,  1878. 


COMPARISON  OF  MISSISSIPPI  AND  NEW  JERSEY  FIRE  CLAYS. 


MISSISSIPPI. 

N.  JERSEY. 

Silica  (Si02  ) 

75.17 

73.25 

Alumina  (A1203  ) 

15.38 

17.33 

Volatile  matter  (H20,  CO2,  etc.)  

3.47 

6.07 

Ferric  oxide  (Fe203  ) 

1.69 

1.16 

Lime  (CaO)  

0.62 

Trace. 

Magnesia  (MeO)  

0.17 

0.14 

Potassa  (K20)  

0.99 

Total  fluxers 

3.26 

2.24 

One  of  the  three  Mississippi  clays 

included  in  the 

average  is  ex- 

tremely  high  in  total  silica  content  (88.52%)  and  deficient  in  alumina 
(5.26%).  The  average  amount  of  silica  in  the  other  two  clays  is  68.50 
per  cent,  and  the  average  amount  of  alumina  is  20.45  per  cent. 

Of  the  more  aluminous  clays  those  numbered  1,  3,  4,  5,  6,  41,  and 
60  were  not  fused  at  the  temperature  required  to  fuse  Seger  cone  No. 
20  (1,530°C).  The  tests  were  preliminary  in  the  preparation  of  a suit- 


24 


CLAYS  OF  MISSISSIPPI 


able  furnace  for  testing  refractory  clays.  More  complete  tests  will 
be  made  and  reported  later. 

Common  Brick  Clays. 

Among  the  geological  formations  of  Mississippi  containing  clays 
suitable  for  the  manufacture  of  common  brick  the  Loess,  Brown  and 
Yellow  Loams  are  the  principal  formations  but  the  residual  clays  from 
nearly  all  the  formations  of  the  state  have  been  employed  for  this 
purpose. 

The  Loess  has  been  the  principal  source  of  brick  material  for  the 
river  and  bluff  towns.  Below  is  given  a rational  analysis  of  a brick 
clay  of  this  formation  at  Vicksburg. 


Total  Silica  60.69 

Clay  Base  20.15 

Sandy  Matter  48.49 

Fluxing  matter  19.59 


This  clay  is  characterized  by  a high  percentage  of  fluxing  impuri- 
ties. It  is  especially  high  in  lime  (8.96)  and  magnesia  (4.56).  It 
has  for  a brick  clay  only  a moderate  amount  of  iron  (3.30%).  Because 
of  this  lack  of  iron  the  burned  bricks  are  brown  instead  of  red.  This 
clay  has  a fair  degree  of  plasticity  and  dries  without  checking.  It 
has  been  used  in  all  the  methods  of  brick  molding,  viz.,  soft-mud, 
stiff-mud  and  dry-pressed.  Under  proper  treatment  the  clay  from  the 
Loess  makes  a good  dry-pressed  brick.  The  clays  of  this  formation 
are  one  of  the  principal  sources  of  brick  material  in  Missouri. 

Yellow  Loam  Clays. — The  clay  most  used  for  brick  in  north- 
western and  central  Mississippi  occurs  at  the  base  of  the  Yellow  Loam 
formation.  Doubtless  in  most  instances  it  belongs  to  that  formation 
but  in  some  deposits  it  may  be  a residual  clay  formed  from  the  under- 
lying formation.  This  clay  has  been  used  in  the  soft-mud  and  the 
stiff-mud  processes  of  moulding.  The  first  named  process  may  be 
used  with  success  in  almost  any  deposit  of  the  clay.  The  latter  is  not 
adapted  to  all  deposits  of  the  clay.  And  again  clay  that  is  suitable 
to  one  kind  of  stiff-mud  machine  may  not  be  at  all  suitable  to  another. 
As  in  the  case  of  the  Brown  Loam  the  surface  stratum  of  the  Yellow 
Loam  is  usually  sandy  and  the  lower  stratum  is  more  clayey.  This 
fact  while  rendering  necessary  careful  selection  of  material  also  renders 
the  tempering  of  the  clay  an  easy  matter. 

A clay  from  this  formation  at  Starkville  has  been  used  by  both 
the  soft-mud  and  the  stiff-mud  processes  and  has  the  following  prop- 
erties: 


MISSISSIPPI  A.  & M.  COLLEGE 


25 


Total  Silica  57.01 

Clay  Base  52.86 

Sandy  Matter  27.01 

Fluxing  Impurities  10.14 


The  above  rational  analysis  shows  that  chemically  this  is  a good 
quality  of  brick  clay.  This  clay  is  now  being  used  it  as  comes  from 
the  pit,  being  run  through  a stiff-mud  machine  without  tempering. 
When  properly  burned  it  forms  a good  hard  brick.  Two  factors  in  the 
geological  occurrence  of  this  clay  may  produce  unsatisfactory  results 
when  the  clay  is  used  directly  from  the  pit  without  care  in  selection. 
In  many  places  the  clay  contains  large  quantities  of  ironstone  con- 
cretions varying  in  size  from  a pea  to  an  egg.  These  concretions  not 
only  cause  flaws  in  the  brick  but  also  frequently  seriously  interfere 
with  the  action  of  the  wires  in  the  cutter.  As  these  concretions  occur 
for  the  large  part  in  streaks  in  the  clay  they  may  be  avoided  by  a little 
care.  Wheverer  the  clay  overlies  limestone  as  it  does  in  the  Prairie 
belt  the  lowermost  part  contains  fragments  or  concretions  of  lime- 
stone. These  also  produce  imperfections  in  the  brick  by  the  slacking 
of  the  lime  in  burning.  If  the  iron  and  the  limestone  are  taken  up 
together  the  latter  acts  as  a flux  to  smelt  the  former.  The  result  is 
that  in  the  hottest  part  of  the  kiln  the  brick  will  be  run  together  in 
a ferruginous  mass.  It  is  best  to  avoid  taking  the  clay  from  immed- 
iately over  the  limestone. 

Another  clay  from  the  above  formation  is  used  in  the  manufacture 
of  brick  at  Laurel.  A rational  analysis  of  this  clay  shows  the  fol- 
lowing to  be  its  constituents: 


Total  Silica  84.86 

Clay  Base  13.38 

Sandy  Matter  78.76 

Fluxing  Matter 4.64 


These  two  clays  represent  the  extremes  of  the  range  in  the  amount 
of  sandy  matter  and  clay  substance  for  the  brick  clays  of  this  for- 
mation. The  first  is  fat  for  a brick  clay,  the  latter  very  lean.  Both 
contain  sufficient  iron  to  produce  a red  color  in  the  brick,  but  since 
the  former  contains  nearly  twice  the  amount  of  iron  of  the  latter  its 
color  is  deeper.  The  latter  dries  much  more  rapidly  than  the  former 
and  requires  more  care  to  prevent  cracking.  The  latter  is  used  in  a 
stiff-mud  machine. 

Brown  Loam  Clay. — In  the  northwestern  part  of  Mississippi 
the  clay  at  the  base  of  the  Brown  Loam  is  used  in  the  manufacture 
of  brick.  All  of  the  processes  of  moulding  have  been  tried  with  success. 
The  clay  varies  in  its  constituent  materials  to  such  an  extent  that  one 


26 


CLAYS  OF  MISSISSIPPI 


method  is  not  adapted  to  all  deposits.  This  fact  makes  it  necessary 
to  test  the  quality  of  the  clay  before  the  installation  of  a plant.  In 
some  localities  the  Brown  Loam  clay  is  entirely  too  lean  for  the  man- 
ufacture of  dry-pressed  brick.  In  nearly  all  deposits  this  is  true  of 
the  upper  stratum. 

A rational  analysis  of  a brick  clay  from  the  Brown  Loam  at  Gre- 
nada exhibits  the  following  results: 


Total  Silica  73.11 

Clay  Base  26.46 

Sandy  Matter  57.09 

Fluxing  Substances  7.78 


This  clay  is  high  in  silica  and  represents  the  sandy  phase  of  the 
Brown  Loam  clay.  In  fluxing  matter  it  shows  a much  smaller  amount 
than  the  Loess  clay.  It  contains  less  lime  and  magnesia  than  the 
latter  and  more  iron.  On  account  of  the  abundance  of  sandy  matter 
it  dries  rapidly  and  requires  care  to  prevent  cracking. 

A Brown  loam  clay  used  for  the  manufacture  of  dry  pressed  brick 
at  Oxford  contains  less  sandy  matter  than  the  above  sample  of  Grenada 
clay  and  a higher  percentage  of  clay  substances.  When  mellowed  and 
mixed  with  water  is  becomes  plastic  to  a fair  degree. 


MISSISSIPPI  A.  & M.  COLLEGE 


27 


Kt  GEOLOCI  CAL  FORMATIONS  OP  NORTHEAST  MISSISSIPPI . ) 

L Devonian  And  Carboniferous . 

1 Potoowc  j DECATUR?  , 

I.  ’ I Tombigbee  A Tetttries  j N E W T\  Q;  N V 

P BeJma  « Tit* 

1*°  ^ Hip  ley 

llll'ffllll  Ugnitie 


Fig.  4. — Map  showing  location  of  Clay  Belts. 


28 


CLAYS  OF  MISSISSIPPI 


THE  GEOLOGICAL  DISTRIBUTION  OF  MISSISSIPPI  CLAYS. 

Nearly  all  of  the  larger  geological  formations  of  the  State  are  clay 
bearing.  In  this  particular,  however,  they  are  not  all  of  equal  im- 
portance. The  following  table  names  the  geological  formations  repre- 
sented in  the  State  and  indicates  the  two  important  clay  belts  treated 
of  in  this  report: 

THE  GEOLOGICAL  FORMATIONS  OF  MISSISSIPPI. 

Recent 


Cenozoic 

f Pleistocene 
| Pliocene 
..  <{  Miocene 

| Oligiocene 
[ Eocene 

Lignitic  Clay  Belt. 

Mesozoic  .... 

f Upper  Cretaceous. 

"1 

[ Lower  Cretaceous 

Potomac  Clay  Belt. 

Paleozoic  .... 

f Lower  Carboniferous. 

J 

••  j 

[ Devonian 

THE  POTOMAC  CLAY  BELT. 

A large  part  of  the  clays  described  in  this  report  belong  to  two 
geological  belts  or  zones;  viz.,  The  Potomac  or  Lower  Cretaceous  and 
the  Lignitic  or  Eocene.  In  each  of  these  belts  the  sub-formations  are 
partly  concealed  by  the  more  superficial  formations  of  the  Lafayette 
(Pliocene)  and  the  Columbia  (Pleistocene).  The  former  contains  in 
many  places  the  same  kinds  of  clays  as  the  sub-formation.  These 
clays  were  derived  from  the  sub-formation  and  redeposited  in  many 
places  in  an  almost  unmodified  condition. 

The  Potomac  clay  belt  occupies  a narrow  belt  extending  through 
the  county  of  Tishomingo  from  North  to  South  along  the  central 
portion  with  some  outliers  of  the  formation  in  the  eastern  portion. 
It  passes  through  the  southeastern  portion  of  Prentiss  county,  through 
central  and  eastern  Itawamba  and  the  northeastern  part  of  Monroe. 

The  Potomac  formation,  the  Eutaw  of  Hilgard  and  the  Tuscaloosa 
of  Smith,  consists  of  gravels  composed  largely  of  chert  derived  from 
the  underlying  Sub-Carboniferous  formation;  of  fine  sands  containing 
clay,  iron  pyrites  and  lignite  in  thin  beds.  The  only  organic  remains 
are  vegetable.  In  many  localities  in  this  belt  the  Potomac  formation 
is  deeply  buried  under  the  sands  or  sandy  clays  of  the  Lafayette  and 
the  Columbia  formations.  As  the  Potomac  formation  was  deeply 
eroded  before  the  deposition  of  the  later  formations  the  line  of  contact 
is  a very  irregular  one.  Moreover,  since  much  of  the  material  of  the 


MISSISSIPPI  A.  & M.  COLLEGE 


29 


Potomac  formation  was  appropriated  and  redeposited  by  Lafayette 
waters  in  a scarcely  modified  form  the  line  of  separation  is  often  obscure. 
The  Lafayette  in  this  belt  is  characterized  by  reddish  or  orange  colored 
sands  and  mottled  clays  containing  in  some  places  ferruginous  clay- 
stones,  or  silicious  ironstones  and  pudding  stones  or  conglomerates 
composed  of  chert  pebbles  and  ferruginous  cerpent. 

Tishomingo  County. 

Goelogy. — The  oldest  geological  formations  of  Tishomingo  county 
and  of  Mississippi  are  the  Devonian  and  the  Lower  Carboniferous 
or  Mississippian  formation.  The  latter  formation  occupies  the  ex- 
treme northeastern  part  of  the  state  and  outcrops  along  the  eastern 
border  of  the  county  from  its  northern  to  its  southern  extremity. 
The  Devonian  underlies  it  along  the  northern  border  of  the  State. 
The  rocks  of  the  formation  are  of  marine  deposition.  They  consist 
of  limestones,  cherts,  shales  and  sandstones.  From  paleontologic 
evidence  it  appears  that  two  of  the  epochs  of  the  Sub-Carboniferous 
are  represented.  These  are  the  Keokuk,  the  St.  Louis  and  possibly 
the  Chester,  though  much  detailed  work  remains  to  be  done  before 
these  beds  are  properly  correlated.  The  rocks  of  this  group  may  be 
observed  in  numerous  out-crops  along  the  course  of  Big  Bear  Creek 
and  the  Tennessee  River. 

The  rocks  of  the  Lower  Carboniferous  were  deeply  eroded  before 
the  deposition  of  later  rocks.  This  period  of  erosion  may  have  extended 
from  the  close  of  the  Carboniferous  to  the  opening  of  the  Lower  Cre- 
taceous though  some  of  the  rocks  of  intervening  periods  may  have  been 
deposited  and  subsequently  removed  by  erosion.  The  rocks  of  the 
Potomac  now  rest  unconformably  upon  the  folded  and  eroded  Mis- 
sissippian rocks.  After  the  deposition  and  elevation  of  the  Potomac 
rocks  another  long  period  of  erosion  was  followed  by  the  deposition 
of  the  Lafayette  rocks.  This  formation  rests  unconformably  upon 
the  Potomac  and  where  the  Potomac  was  never  deposited  or  was  de- 
posited and  removed  by  erosion  upon  the  Lower  Carboniferous  rocks. 

The  Lafayette  was  in  turn  eroded  and  the  Columbia  deposited. 
In  places  the  latter  formation  rests  upon  the  Carboniferous,  in  others 
upon  the  Potomac  and  still  in  others  upon  the  Lafayette. 

The  argillaceous  products  of  the  Carboniferous  are  some  slate 
colored  shales  whose  economic  value  as  cement  or  vitrified  brick  ma- 
terial is  yet  to  be  investigated. 

The  Potomac  formation  of  Tishomingo  county  consists,  at  the 
base,  of  a bed  of  gravel  succeeded  by  alternate  beds  of  micaceous  sands 


30 


CLAYS  OF  MISSISSIPPI 


and  variegated  clays  The  clays  vary  greatly  in  color  and  texture. 
Some  are  pure  white,  others  red,  cream,  yellow  or  slate  colored.  Some 
doubtless  owe  their  color  to  percolations  of  iron  from  the  Lafayette. 
Thin  layers  of  lignite  occur  in  some  of  the  beds.  The  white  clay  which 
in  some  places  has  sufficient  clay  base  and  freedom  from  impurities 
to  warrant  its  use  in  the  manufacture  of  white  ware,  is  in  other  places 
an  impure  bed  of  silica.  The  silica  is  in  a very  finely  divided  state, 
and  like  the  clay  is  white  in  color.  It  is  derived  from  the  chert  beds 
of  the  Carboniferous  which  is  also  the  origin  of  the  chert  gravel.  The 
gravel  becomes  an  important  water  bearing  stratum  in  the  bordering 
counties.  The  clay  may  in  part  at  least  have  been  derived  from  the 
shale  of  the  carboniferous  and  the  sand  from  the  grayish  sandstone 
of  that  group. 

The  Potomac  formation  occupies  the  central  and  southwestern 
parts  of  the  county  as  the  sub-formation.  Outliers  also  occur  in  the 
above  described  Carboniferous  area,  doubtless  in  the  synclinal  troughs 
of  that  area.  Only  in  isolated  areas  where  the  surficial  deposits  of 
Lafayette  and  Columbia  have  been  removed  by  erosion  is  the  Potomac 
exposed. 

The  Tombigbee  sands  of  the  Upper  Cretaceous  occupy  the  re- 
mainder of  Tishomingo  county  as  its  sub-formation.  This  formation 
consists  for  the  most  part  of  micaceous  sands  containing  iron  pyrites, 
lignitized  wood,  impure  clays  and  fossils.  As  in  the  case  of  the  older 
formations  it  is  largely  covered  by  deposits  of  Lafayette  and  Columbia. 
The  combined  thickness  of  the  Tombigbee  and  Potomac  at  Corinth  as 
ascertained  by  a well  record  is  425  feet.  Well  records  at  Amory  which 
is  near  the  line  of  contact  of  the  two  formations  give  a thickness  of  210 
feet  for  the  Potomac. 

The  Lafayette  which  is  the  principal  surficial  formation  of  the 
county  consists  of  beds  of  gravel  and  chert  which  have  been  derived 
from  the  Potomac  and  the  Carboniferous,  of  sands,  of  clays  of  various 
colors  and  of  irregular  layers  of  ironstone.  The  gravel  and  chert  are 
in  many  places  firmly  cemented  by  a ferruginous  cement  into  a con- 
glomerate. These  beds  are  one  of  the  principal  sources  of  road  metal 
not  only  for  the  county  but  for  the  northern  part  of  the  state.  The 
clays  are  in  some  places  but-little-modified  clays  of  the  Potomac 
and  the  transition  is  so  gradual  as  to  render  it  almost  if  not  quite  im- 
possible to  mark  the  line  of  separation.  The  beds  are  stratified  in 
many  places  and  contain  thin  irregular  layers  of  ironstone  of  variable 
thickness  but  rarely  in  excess  of  six  inches. 

The  Yellow  loam,  Columbia,  formation  of  Tishomingo  county  is 


MISSISSIPPI  A.  & M.  COLLEGE 


31 


so  closely  associated  with  the  underlying  Lafayette  that  it  seems,  in 
places,  merely  a disintegration  product  of  the  latter.  In  other  places 
although  very  similar  in  its  physical  properties,  it  is  more  clearly 
separated  from  the  Lafayette  than  at  any  other  point  in  Mississippi. 
On  Big  Cripple  Deer  Creek  and  on  the  west  bank  of  Big  Bear  Creek  the 
following  stratigraphical  conditions  are  exposed: 

1.  Soil  (Top). 

2.  Fine  red  sand,  containing  in  the  lower  part,  rounded  pebbles 

(Columbia).  * 0$j  *\ 

3.  Coarser,  reddish  to  orange  colored  sand  with  some  white  streaks 
and  at  the  base  a thick  bed  of  chert  pebbles  with  some  water-worn 
(Lafayette) . 

The  upper  bed  of  pebbles  was  noticed  in  a number  of  places  and 
always  at  or  near  the  apex  of  the  hills  or  ridges  while  below  were  un- 
doubted Lafayette  rocks.  The  pebbles  in  respect  to  their  worn  con- 
dition resemble  the  Lafayette  pebbles  in  the  Southern  part  of  the  State. 

Clays  of  Tishomingo. 

The  clays  of  this  county  are  of  considerable  extent  and  importance. 
The  best  deposits  of  clay  belong  to  the  Potomac  formation.  The 
shales  belong  to  the  Lower  Carboniferous.  Clays  from  the  following 
localities  were  selected  for  study. 

Clay  No.  1. 

At  Penniwinkle  Hill,  four  miles  south  of  Iuka,  the  following 
geological  section  is  exposed: 

1.  Blue  micaceous  clay  changing  to  yellow,  5 feet  (top). 

2.  Crav,  laminated  micaceous  clay  with  thin  iron  stone  layers, 
20  feet. 

3.  White,  massive,  jointed  clay,  15  feet. 

The  first  bed  is  a transition  to  Lafayette  which  lies  at  a higher 
level  and  back  from  the  brow  of  the  hill.  The  clay  at  the  base  is  prob- 
ably Potomac  though  its  determination  is  based  entirely  upon  strati- 
graphic conditions. 

The  chemical  composition  of  the  clay  is  as  follows: 

ULTIMATE  ANALYSIS. 


Moisture  1.09 

Loss  on  Ignition  7.34 

Silica  (Si02  ) 68.65 

Ferric  Oxide  (Fe2  03  ).. 2.77 

Alumina  (Al>  03  ) 18.99 

Lime  (CaO)  20 

Magnesia  (MgO)  20 

Sulphur  Trioxide  (SO3  ) Trace. 


32 


CLAYS  OF  MISSISSIPPI 


RATIONAL  ANALYSIS. 


Clay  Base  48.12 

Free  Silica  (Si02)  39.52 

Fluxing  Impurities 3.17 


In  its  physical  characters  it  is  a white  plastic  clay  having  a spe- 
cific gravity  of  2.67.  The  air-dried  briquettes  exhibit  a tensile  strength 
of  36  pounds  in  the  average  and  of  40  pounds  in  the  maximum  per 
square  inch.  The  grain  is  of  medium  size.  The  amount  of  water 
required  to  render  the  clay  plastic  was  25  per  cent,  of  its  weight. 

The  air  shrinkage  of  the  briquettes  was  6 per  cent.  The  fire 
shrinkage  is  2 per  cent.  The  color  of  the  burnt  clay  varies  from  white 
to  cream.  The  clay  may  be  fashioned  into  vessels  which  burn  hard 
and  white  without  checking  or  cracking.  It  may  be  used  for  stoneware, 
whiteware  and  fire  brick.  Although  its  total  fluxing  impurities  is 
high  yet  it  is  refractory  to  above  1,630  degrees.  However,  the  clay 
has  distributed  through  it  small  silicious  pebbles  and  these  should 
be  removed  by  crushing  so  as  to  prevent  imperfections  in  the  ware. 

Clay  No.  2. 

The  grayish  clay  from  the  upper  stratum  of  the  above  section  has 
the  following  physical  characters.  It  contains  much  muscovite,  the 
crystals  of  which  are  numerous  and  visible  to  the  unaided  eye.  In 
water  it  disintegrates  rapidly  into  small  flakes.  The  air-dried  briquettes 
have  an  average  tensile  strength  of  65  pounds  per  square  inch  and  a 
maximum  of  70  pounds.  They  shrink  in  air-drying  4 per  cent. 

It  burns  to  a dense  strong  body  and  doubtless  can  be  used  with 
success  for  the  common  grades  of  stoneware. 

Clay  No.  3. 

This  clay  occurs  in  the  public  road  two  miles  south  of  Old  East- 
port.  The  outcrop  is  about  five  feet  in  thickness  and  is  partly  con- 
cealed by  Lafayette  on  the  right  of  the  outcrop.  The  chemical  com- 
position of  the  clay  is: 


ULTIMATE  ANALYSIS. 

Moisture  58 

Loss  on  Ignition  4.78 

Silica  (Si()2  ) 79.23 

Ferric  Oxide  (Fe203  ) 67 

Alumina  (Al2  03  ) 13.91 

Lime  (CaO)  59 

Magnesia  (MgO)  21 

Sulphur  Trioxide  (S03  ) Trace. 

RATIONAL  ANALYSIS. 

Clay  Base  48.23 

Free  Silica  41.36 

Fluxing  Impurities  1.47 


MISSISSIPPI  A.  & M.  COLLEGE 


33 


The  average  tensile  strength  of  the  clay  is  50  pounds 
per  square  inch.  Its  specific  gravity  ranges  from  2.48 
to  2.64.  The  amount  of  water  required  to  render  it 
plastic  was  about  33  per  cent,  of  its  weight. 

In  water  it  slacks  rapidly  to  medium  size  flakes.  The 
air-shrinkage  is  2 per  cent.  The  free  silica  is  in  a finely 
divided  state. 

This  clay  remained  unfused  at  the  fusion  point  of 
cone  No.  20. It  is  without  doubt  a refractory  clay. 
When  fashioned  and  burned  in  the  form  of  a vessel  it 
produced  a strong  white  body  without  checks  or 
crazes. 

Clay  No.  4. 

Another  white  clay  from  the  R.  W.  Peden  farm 
south  of  Iuka.  This  clay  contains  much  silica  in  a 
finely  divided  state.  The  silica  was  doubtless  derived 
from  the  beds  of  that  nature  which  occur  in  con- 
nection with  the  Sub-Carboniferous  chert. 

When  mixed  with  one-third  its  weight  of  water  the 
clay  becomes  plastic.  It  has  a specific  gravity  vary- 

Fig.  5 — Section  at*7  r ^ & J 

penniwmkie  Hill,  ing  from  2.51  to  2.60.  4 he  average  tensile  strength 

of  its  air-dried  briquettes  is  40  pounds  per  square  inch. 

Its  chemical  analysis  is: 


ULTIMATE  ANALYSIS. 


Moisture 48 

Loss  on  Ignition  4.82 

Silica  (Si()2  ) 80.03 

Ferric  Oxide  (Fe203  ) 1.68 

Alumina  (A1203  ) 12.00 

Lime  (CaO)  26 

Sulphur  Trioxide  (S03  ) Trace. 

RATIONAL  ANALYSIS. 

Clay  Base  30.41 

Free  Silica  61 .62 

Fluxing  Impurities  2.18 


In  a preliminary  test  on  fusibility  it  was  not  fused  at  the  tempera- 
ture required  to  fuse  cone  No.  20.  The  body  of  the  burned  clay  was 
white  and  hard. 

Clay  No.  5. 


A white  clay  from  M.  C.  Hill's  farm  occurring  under  conditions 
similar  to  the  above.  It  is  a plastic  clay  when  mixed  with  about 
thirty  per  cent,  of  water.  It  slacks  rapidly  in  water  to  fine  grains. 


34 


CLAYS  OF  MISSISSIPPI 


Fig.  6. — Stiff-Mud  Auger  Brick  Machine,  end  cut. 


MISSISSIPPI  A.  & M.  COLLEGE 


35 


The  average  tensile  strength  of  its  air-dried  briquettes  is  30  pounds 
per  square  inch.  When  air  dried  it  shrinks  2 per  cent.  It  withstood 
a temperature  higher  than  that  required  to  fuse  Seger  cone  No.  20 
which  fuses  about  1,530  degrees  C. 

Clay  No.  6. 

A white  clay  very  similar  to  No.  5 occurs  on  the  James  Turner 
farm.  It  has  the  following  chemical  composition: 

ULTIMATE  ANALYSIS. 


Moisture 59 

Loss  on  Ignition  8.00 

Silica  (Si02  ) 66.85 

Ferric  Oxide  (Fe2  O3  ) 3.77 

Alumina  (Al2  O3  )- 20.54 

Lime  (CaO)  21 

Magnesia  (MgO)  „ 18 

Sulphur  Trioxide  (S03  ) Trace. 

RATIONAL  ANALYSIS. 

Clay  Base  52.05 

Free  Silica  35.34 

Fluxing  Impurities 4.16 


The  clay  is  plastic  when  mixed  with  about  30  per  cent,  of  water. 
Its  average  specific  gravity  is  2.62.  On  drying  in  the  air  it  shrinks 
4 per  cent.  The  average  tensile  strength  is  35  pounds  per  square  inch. 
In  water  it  slacks  rapidly  to  grains  of  medium  size. 

Unfused  at  temperature  required  to  fuse  cone  No.  20.  Body  of 
the  burned  clay,  hard,  firm  and  white  in  color. 

Clay  No.  7. 

Is  a light  red  clay  from  the  same  locality  and  geological  horizon. 
It  has  a specific  gravity  of  2.61.  When  placed  in  water  it  slacks  read- 
ily to  a fine  grain.  The  air-dried  briquettes  have  an  average  tensile 
strength  of  28  pounds  per  square  inch.  The  clay  requires  32  per  cent, 
of  water  to  render  it  plastic.  Its  air-shrinkage  is  5 per  cent. 

Clay  No.  8. 

This  is  a dark  gray  clay  from  near  Short  Post  Office.  The  specific 
gravity  of  the  clay  varies  from  1.92  to  2.07.  In  water  it  slacks  rapidly 
to  fine  grains.  The  tensile  strength  of  its  air  dried  briquettes  is  64 
pounds  per  square  inch  on  the  average.  The  amount  of  water  required 
to  produce  plasticity  is  30  per  cent.  On  drying  in  the  air  the  clay 
shrinks  7 per  cent. 

The  clay  contains  muscovite  crystals  which  are  visible  to  the  un- 
aided eye.  It  also  contains  lignite  and  a few  small  white  pebbles. 


36 


CLAYS  OF  MISSISSIPPI 


Clay  No.  9. 

A red  clay  occurs  on  the  R.  F.  Thorne’s  farm  north  of  Iuka  about 
six  miles.  The  stratum  has  a thickness  of  15  feet  and  occurs  at  the 
base  of  the  Lafayette  though  it  probably  belongs  to  the  Potomac. 
It  is  a light  red  clay  containing  concretionary  masses  of  a deeper  red 
or  in  some  instances  pure  white. 

The  clay  has  the  following  chemical  composition: 

ULTIMATE  ANALYSIS. 


Moisture 87 

Loss  on  Ignition  11.96 

Silica  (Si(>2  ) - 38.11 

Ferric  Oxide  (Fe2  03  ).. 11.73 

Alumina  (Al2  03  )„ 36.42 

Lime  (CaO)  60 

Magnesia  (MgO)  14 

Sulphur  Trioxide  (S03  ). Trace. 


RATIONAL  ANALYSIS. 


Clay  Base  92.20 

Free  Silica  00.00 

Fluxing  Impurities 12.47 


The  specific  gravity  is  2.54.  It  slacks  readily  in  water  to  a medium 
grain.  The  average  tensile  strength  is  26  pounds  per  square  inch. 
The  air-shrinkage  amounts  to  4 per  cent.  Plasticity  is  attained  by  the 
use  of  30  per  cent,  of  water. 

■ The  amount  of  iron  in  this  clay  is  high  and  it  makes  a very  good 
ochre  in  some  places.  It  has  been  used  locally  for  paint. 

The  amount  of  fluxing  impurities  prohibit  its  use  as  a brick  or 
potters  clay. 

Clay  No.  10. 

At  the  base  of  an  outcrop  of  laminated  clays  interstratified  with 
thin  layers  of  sand  near  the  fish  pond  at  Iuka  there  is  a light  red  clay 
which  has  the  following  chemical  composition: 


ULTIMATE  ANALYSIS. 


Moisture  58 

Loss  on  Ignition  5.20 

Silica  (SiO  > ) 70.81 

Ferric  Oxide  (F2  03  ) 11.20 

Alumina  (Al2  03  ) 11.20 

Lime  (CaO)  60 

Magnesia  (MgO)  50  • 

Sulphur  Trioxide  (S03  ) Trace. 


RATIONAL  ANALYSIS. 


Clay  Base  28.00 

Free  Silica  53.86 

Fluxing  Impurities 12.30 


MISSISSIPPI  A.  & M.  COLLEGE 


Fig  7— A Pug  Mill. 


38 


CLAYS  OF  MISSISSIPPI 


The  laminated  clays  of  the  outcrop  are  of  variable  colors,  bluish 
gray  predominating.  The  interstratified  sands  contain  many  mus- 
covite crystals  and  streaks  of  ochre.  A platy  cleavage  is  well  developed 
in  some  layers  of  the  clay.  In  the  upper  layers  the  clay  is  more  sandy 
and  the  color  more  uniformly  yellow. 

The  lowermost  clay  has  a specific  gravity  of  2.48  to  2.64.  It 
slacks  rapidly  in  water  to  medium  grains.  The  average  tensile  strength 
of  the  air  dried  briquettes  is  30  pounds  per  square  inch.  Twenty-five 
per  cent,  of  water  is  required  to  render  the  clay  plastic.  The  air- 
shrinkage  is  5 per  cent. 

Clays  of  Itawamba  County. 

Geology. — The  extreme  northeastern  part  of  the  county  has  for 
its  sub-formation  the  Lower  Carboniferous.  The  central  and  eastern 
parts  of  the  county  is  occupied  by  the  Potomac  and  the  western  part 
by  the  Tombigbee  formation.  Resting  upon  these  formations  every- 
where except  where  removed  by  erosion,  the  Lafayette  and  Cloumbia 
are  found.  The  topography  of  the  divide  between  the  Bear  Creek 
drainage  system  and  that  of  the  Tombigbee  is  of  a rugged  type.  The 
ridges  and  hills  are  composed  of  Potomac  clays  and  sands  and  are  capped 
with  the  red  or  orange  colored  sands  of  the  Lafayette  which  contain 
in  many  places  irregular  layers  of  ironstone.  Beds  of  lignite  of  con- 
siderable thickness  are  found  in  the  clays  of  the  former. 

Clay  No.  11. 

At  Miston  on  the  James  Davidson  place  there  is  an  exposure  of 
mottled  clay  which  is  cream  colored  when  reduced  to  powder.  The 
predominate  colors  are  red,  purple,  and  white.  There  is  about  five 
feet  of  this  clay  resting  under  some  thin  layers  of  ironstone  which  have 
lying  above  them  about  six  feet  of  thin  bedded  sands  and  clays. 

The  chemical  composition  of  the  mottled  clay  is: 

ULTIMATE  ANALYSIS. 


Moisture 54 

Loss  on  Ignition  7.40 

Silica  (Si02  ) 59.12 

Ferric  Oxide  (F2  O3  ) 4.39 

Alumina  (Al2  O3  ) 27.44 

Lime  (CaO)  34 

Magnesia  (MgO)  28 

Sulphur  Trioxide  (S03  ) Trace. 

RATIONAL  ANALYSIS. 

Clay  Base  69.54 

Free  Silica  (sandy  matter) 17.02 

Fluxing  Impurities 5.01 


MISSISSIPPI  A.  & M.  COLLEGE 


39 


The  clay  becomes  plastic  when  mixed  with  25  per  cent,  of  water 
and  shrinks  on  air-drying  8 per  cent.  It  has  a specific  gravity  of  2.50. 
In  water  it  slacks  at  a medium  rate  to  a small  flake.  The  average 
tensile  strength  of  the  clay  is  80  pounds  and  the  maximum  94  pounds 
per  square  inch.  It  is  slightly  gritty  to  the  feel;  distinctly  so  to  the 
taste.  Muscovite  crystals  are  present  and  visible  to  the  unaided  eye. 

This  clay  has  been  used  for  a number  of  years  by  Mr.  Davidson  in  a 
small  hand  pottery.  It  has  been  used  in  the  manufacture  of  churns,  jugs 
and  jars,  flower  pots  and  tombstones.  He  has  two  kilns,  each  having 
a capacity  of  650  gallons.  The  kilns  are  the  up-draught  type.  They 
are  made  of  clay  and  the  native  red  sandstone  or  ironstone  of  the 
Lafayette.  Wood  is  the  fuel  used  in  burning.  The  clay  is  used  as  it 
comes  from  the  pit  without  washing.  It  is  first  mixed  in  a small 
pug  mill  turned  by  horse  power.  It  is  then  moulded  by  hand  into 
balls  of  a given  weight,  the  weight  varying  with  the  size  of  the  desired 
vessel. 

A ball  of  clay  is  placed  upon  the  surface  of  an  horizontal  wheel 
which  is  made  to  rotate  by  “kicking”  a lever.  The  turner  while  kick- 
ing the  lever  with  his  foot  fashions  the  clay  with  his  hands  into  jug, 
jar  or  churn.  The  height  of  the  vessel  is  measured  on  a vertical  guage 
and  its  diameter  on  an  horizontal  guage  so  arranged  as  to  be  brought 
over  the  vessel  at  will.  When  the  vessel  is  completed  it  is  cut  free  from 
the  wheel  by  the  use  of  a wire  which  is  held  near  the  surface  while  the 
wheel  is  rotating.  Small  vessels  may  be  lifted  directly  from  the  wheel 
by  the  operator.  In  removing  large  vessels  thin  metal  lifters  are 
clasped  around  the  bottom  of  the  vessel  to  aid  in  its  removal. 

In  the  small  hand  potteries  the  vessels  are  dried  by  placing  them 
on  tables  or  shelves  and  allowing  them  to  dry  in  the  air.  This  is  a 
slower  process  than  kiln,  or  steam  drying. 

Mr.  Davidson  uses  the  Albany  “slip”  clay  to  glaze  his  ware.  This 
clay  gives  a brown  glaze  to  the  ware.  It  is  a natural  clay  which  has  a 
lower  fusibility  than  ordinary  clay.  The  chemical  composition  of  a 
sample  of  the  slip  clay  is: 


Silica  56.75 

Alumina 15.47 

Loss  on  Ignition  8.87 

Moisture 0.37 

Ferric  Oxide  5.73 

Lime 5.78 

Magnesia  3.32 

Potash  and  Soda  3.25 


When  the  vessel  is  dry  it  is  dipped  in  or  sprayed  with  the  slip  clay 
solution  and  then  placed  in  the  kiln  for  burning. 


40 


CLAYS  OF  MISSISSIPPI 


The  total  shrinkage  is  about  7 per  cent,  of  which  amount  5 per 
cent,  is  air-shrinkage.  The  product  of  the  kiln  when  unglazed  is 
cream  colored,  hard  and  dense. 

Clay  No.  12. 

xAbout  three  miles  south  of  Miston  is  the  clay  pit  of  Mr.  E.  P. 
Kennedy.  The  pit  is  near  the  public  road  and  the  outcrop  shows 
four  or  five  feet  of  mottled  clay,  white  predominating.  At  several 
points  between  Miston  and  this  pit  the  white  and  purple  clays  of  the 
Potomac  formation  are  exposed  at  the  base  of  the  ridges  which  are 
capped  or  largely  composed  of  Lafayette.  The  latter  being  composed 
of  sands,  impure  clays  and  thin  beds  and  concretionery  masses  of  fer- 
ruginous stone. 

Mr.  Kennedy  uses  the  clay  in  a small  hand  pottery.  He  has  a 
small  up  draught  kiln  in  which  wood  is  used  as  fuel.  He  manufactures 
jugs,  jars,  churns,  etc.  The  Albany  slip  glaze  is  used. 

The  chemical  composition  of  the  Kennedy  clay  is: 


ULTIMATE  ANALYSIS. 

Moisture  2.71 

Loss  on  Ignition  5.91 

Silica  (Si02  ) 71.53 

Ferric  Oxide  (Fe2  03  ).. 4.14 

Alumina  AL  03  ) 14.46 

Lime  (CaO)  62 

Magnesia  (MgO)  55 

Sulphur  Trioxide  (S03  ) 00.00 

RATIONAL  ANALYSIS. 

Clay  Base  36.64 

Free  Silica  49.35 

Fluxing  Impurities 5.31 


The  clay  has  a specific  gravity  of  2.50.  It  slacks  in  water  with 
moderate  rapidity  to  a medium  size  flake.  The  maximum  tensile 
strength  is  125  pounds  per  square  inch.  It  requires  about  30  per  cent, 
of  water  to  render  it  plastic  and  shrinks  on  drying  8 per  cent. 

Clay  No.  13. 

This  clay  occurs  on  the  Summerford  farm  about  three  and  one- 
half  miles  south  of  Miston.  The  clay  is  used  by  Mr.  W.  A.  Summer- 
ford  in  a small  hand  pottery.  The  clay  is  a white  joint  clay,  smooth 
to  the  feel  but  gritty  to  the  taste.  The  clay  in  the  pit  has  a thickness 
of  three  feet.  The  pit  has  not  been  dug  to  the  bottom  of  the  clay  bed. 

The  average  specific  gravity  of  the  clay  is  2.43.  It  slacks  slowly 
in  water  to  rather  coarse  grains.  It  requires  about  30  per  cent,  of 
water  to  make  it  plastic.  The  average  tensile  strength  of  the  air  dried 


MISSISSIPPI  A.  & M.  COLLEGE  41 

briquettes  is  111  pounds  and  its  maximum  strength,  125  pounds  per 
square  inch.  It  has  an  air-shrinkage  of  8 per  cent. 

The  chemical  composition  of  a sample  of  the  clay  is  as  follows: 


ULTIMATE  ANALYSIS. 

Moisture  77 

Loss  on  Ignition  6.77 

Silica  62.58 

Ferric  Oxide  1.57 

Alumina 27.58 

Lime  40 

Magnesia  Trace. 

Sulphur  Trioxide  T race. 

RATIONAL  ANALYSIS. 

Clay  Base  69.89 

Free  Silica  20.27 

Fluxing  Impurities 1.97 


Clay  No.  14. 

A white  clay  belonging  to  the  Potomac  formation  outcrops  on  the 
farm  of  William  Reed,  one-half  mile  east  of  Reedville.  This  clay 
slacks  readily  in  water  to  a fine  grain  and  may  be  rendered  plastic  by 
the  addition  of  30  per  cent,  of  water. 

A chemical  analysis  of  the  clay  gave  the  following  results: 


ULTIMATE  ANALYSIS. 

Moisture 3.03 

Loss  on  Ignition  6.66 

Silica  66.70 

Ferric  Oxide  3. 10 

Alumina  18.22 

Lime  57 

Magnesia  47 

Sulphur  Trioxide  .22 

RATIONAL  ANALYSIS. 

Clay  Base  46.17 

Free  Silica  38.75 

Fluxing  Impurities 4.14 


This  clay  has  a specific  gravity  of  2.50.  Burns  hard  and  dense. 
Was  unfused  at  temperature  required  to  fuse  Cone  No.  14.  Is  a good 
stoneware  clay. 

Clay  No.  15. 

This  clay  is  from  an  outcrop  at  the  point  where  the  Raper  Springs 
road  crosses  Spring  creek.  The  following  geological  section  is  exposed: 

1.  Lafayette  sand,  10  feet. 

2.  Rocks  concealed  for  15  feet. 

3.  Blue  clay,  4 feet. 

4.  Sand  and  thin  sandstone,  10  feet. 

5.  Sandstone  containing  some  clay,  2 feet. 

6.  Blue  clay  (bottom),  6 feet. 


42 


CLAYS  OF  MISSISSIPPI 


Farther  back  from  the  creek  at  a higher  level  Lafayette  gravels 
occur  and  at  a still  higher  level  a reddish  sandy  clay  is  covered  with 
the  yellowish  loam  of  the  Columbia. 

The  bluish  clay  at  the  base  of  the  outcrop  has  a specific  gravity 
of  2.47.  In  water  it  slacks  slowly  to  a coarse  grain.  The  average 
tensile  strength  of  the  air-dried  briquettes  is  113  pounds  and  the  max- 
imum is  120  pounds  per  square  inch.  The  clay  requires  the  addition 
of  32  per  cent,  of  water  to  render  it  plastic.  In  drying  in  the  air  it 
shrinks  7 per  cent.  The  fire-shrinkage  is  about  2 per  cent.  It  vitri- 
fies at  Cone  5.  Will  take  either  salt  or  slip  glaze  and  can  be  used  for 
stoneware  purposes. 

THE  LIGNITIC  CLAY  BELT. 

The  Lignitic  (Eocene)  clay  belt  extends  from  the  Tennessee  line 
on  the  northern  border  of  Marshall  county  to  the  Alabama  line  on  the 
eastern  border  of  Lauderdale  county.  It  includes  the  whole  or  parts 
of  the  following  counties:  Marshall,  DeSoto,  Benton,  Lafayette, 
Panola,  Yalobusha,  Calhoun,  Grenada,  Webster,  Chickasaw,  Choctaw, 
Montgomery,  Winston,  Noxubee,  Kemper,  and  Lauderdale.  That 
portion  of  the  Lignitic  from  which  the  majority  of  the  specimens  were 
taken  does  not  include  the  Flatwoods  division.  The  specimens  of 
clay  studied  came  in  a large  measure  from  one  of  the  minor  subdivis- 
ions of  the  Lagrange  of  Hilgard.  The  best  clays  of  the  Lignitic  belt 
are  found  along  a line  passing  through  the  central  part  of  the  outcrop 
of  the  formation,  from  north  to  south. 

In  extent  and  quality  of  the  clay  this  is  the  most  important  clay 
belt  in  the  State. 

Here  as  in  the  Potomac  clay  belt  we  find  difficulty  in  attempting 
to  definitely  delimit  the  surficial  deposits  of  Lafayette  and  Columbia. 
The  Lafayette  formation  composed  in  a large  measure  of  Lignitic- 
Eocene  sands  and  clays  and  re-deposited  so  as  to  form  in  many  places 
a gradual  transition  from  the  older  to  the  younger  formation,  presents 
many  perplexing  stratigraphical  problems.  The  absence  of  fossils 
over  a greater  part  of  the  area  adds  to  the  difficulties. 

The  Lagrange  in  its  eastern  and  southern  area  contains  marine 
fossils  which  aid  in  delimiting  it.  In  its  northern  portion  it  contains 
in  some  outcrops  fossil  leaves.  Beds  of  lignite  are  of  frequent  occur- 
rence throughout  its  area.  These  latter  make  possible  local  lines  of 
separation. 


MISSISSIPPI  A.  & M.  COLLEGE 


43 


Fig.  8 — Pottery  of  the  Holly  Spring’s  Stoneware  and  Fire  Brick  Co.,  Holly  Springs,  Miss. 


44 


CLAYS  OF  MISSISSIPPI 


The  Lignitic-Eocene  is  composed  of  two  fairly  well  differentiated 
formations,  viz.:  the  Flatoowds  clay  (Hilgard),  or  Sucranochee  (John- 
son), and  the  Lagrange  (Hilgard).  The  first  formation  is  comparatively 
homogenous  as  regards  structure  and  kind  of  material  and  there  seems 
little  necessity  for  further  dividing.  In  the  greater  part  of  its  outcrops 
it  is  a grayish  laminated  clay  which  is  shale-like  in  some  outcrops.  It 
weathers  to  a brownish  red,  especially  in  the  upper  horizons,  and  to 
a lighter  gray  in  the  lowermost  strata. 

In  the  upper  layers  more  iron  is  present  in  the  clay  and  ironstone 
layers  or  nodules  are  of  frequent  occurrence.  Fossils  of  any  kind  are 
rare. 

The  Lagrange-Eocene  is  heterogenous  in  composition.  It  is  made 
up  of  a series  of  clays,  sands  and  lignites  which  vary  greatly  in  thick- 
ness and  uniformity  of  material.  Minor  subdivisions  for  given  locali- 
ties are  possible.  But  whether  any  stratum  or  series  of  strata  will 
be  found  to  have  the  continuity  of  the  Flatwoods  is  questionable. 
The  Lagrange  formation  contains  fossils  of  both  vegetable  and  animal 
origin  and  beds  of  rock  deposited  under  marine,  fresh  and  brackish 
water  conditions. 

The  general  stratigraphic  relations  of  the  Lignitic  clay  belt  forma- 
tions are  as  follows: 

The  Flatwoods-Eocene  rests  upon  the  eroded  surface  of  the  Ripley- 
Cretaceous  or  the  Selma-Cretaceous. 

The  Lagrange  overlies  the  Flatwoods  conformably.  These  two 
form  the  sub-formations  of  this  clay  province. 

The  Lafayette  lies  unconformably  upon  these  sub-formations. 

The  Columbia  lies  unconformably  upon  all  of  the  foregoing  except 
where  it  has  been  removed  by  erosion.  In  the  northern  part  of  the 
area  this  formation  is  called  the  Brown  Loam  and  in  the  southern  part 
it  is  called  the  Yellow  Loam.  Color  seems  to  be  the  principal  distinction 
in  some  places.  Both  vary  in  texture  and  chemical  composition. 

Marshall  County. 

Geology. — The  sub-formation  of  Marshall  county  is  the  Lignitic- 
Eocene.  This  formation  consists  largely  of  clays  and  sands.  The 
clays  are  fossil-leaf  bearing  in  some  places  and  when  thus  found  in 
laminated  beds  of  considerable  extent  they  may  be  distinguished  from 
the  Lafayette  formation  which,  because  much  of  its  material  has  been 
derived  from  the  Lignitic,  is  in  many  places  difficult  to  separate  from 


MISSISSIPPI  A.  & M.  COLLEGE 


45 


the  older  formation.  In  many  places  clays  and  sands  from  the  Lig- 
nitic  have  been  re-deposited  by  Lafayette  waters  in  an  apparently  but 
little  disturbed  condition. 

It  is  of  course  entirely  possible  that  fossil  leaves  or  shells  may 
have  been  thus  re-deposited  in  small  masses  of  clay;  so  that  the  mere 
presence  of  Lignitic  fossils  is  not  conclusive  evidence  of  the  Lignitic 
age  of  the  deposit. 

However,  it  is  not  probable  that  large  masses  of  clay  were  so  re- 
deposited; hence,  the  presence  of  fossils  in  large  masses  of  clay  or  in 
sands  underlying  such  masses  of  clay  may  be  taken  as  evidence  of  the 
age  of  the  beds. 

Again,  since  the  Lafayette  was  deposited  upon  the  eroded  surface 
of  the  Lignitic,  in  some  places  the  bedding  planes  of  the  two  formations 
are  discordant  and  their  separation  rendered  much  less  difficult. 

The  Lagrange  division  of  the  Lignitic  occupies  the  greater  part 
of  the  sub-surface  of  this  county.  The  clays  of  the  Lagrange  vary 
much  in  color  but  white,  cream  and  pink  are  the  prevailing  colors. 
In  some  places  they  are  laminated  and  interstratified  with  thin  beds 
of  sand;  in  others  they  are  jointed  and  massive. 

The  sands  are  of  various  colors,  being  frequently  orange,  red  or 
pink.  They  contain  thin  layers  of  ferruginous  rock  and  hollow  iron- 
stone concretions  of  various  shapes. 

The  surficial  formations  of  Marshall  county  are  the  Lafayette  and 
the  Brown  Loam  (Columbia). 

There  is  no  well-marked  line  of  separation  for  these  formations. 
In  the  majority  of  outcrops  there  is  a gradual  transition  from  the 
Lafayette  to  the  Columbia  both  in  appearance  and  in  character  of  the 
material.  The  Lafayette  formation  is  composed  largely  of  sands  and 
thin  beds  of  white  or  tinted  clays.  The  sands  are  usually  orange, 
red  or  yellow  in  color.  Their  composition  is  largely  quartz  and  mica 
grains  covered  with  a thin  layer  of  ferric  oxide.  Apparently  the 
greater  part  of  the  material  of  this  formation  has  been  derived  from 
the  underlying  Lignitic. 

The  Columbia  consists  of  a brown  sandy  loam  which  is  usually 
more  argillaceous  at  the  bottom  of  the  deposit  and  unstratified  in  all 
parts. 


46 


CLAYS  OF  MISSISSIPPI 


The  following  record  of  the  Holly  Springs 
well  reveals  the  local  stratigraphical  conditions: 


1.  Reddish  brown  clay  20 

2.  Red  sand,  coarse  87 

3.  Sandy  rock 

4.  Clay  .. 

5.  Hard  sandstone . 5 

6.  Clay  and  sand  140 

7.  Sand,  fine,  water-bearing 40 

8.  Pipe  clay  13 

9.  Coarse  sand  4 

10.  Sticky  clay  .. 43- 1 

Total  depth  400.6 


20 

ft.  \ 

87 

ft.  [ 

1.1 

ft.  1 

52 

ft. 

5 

ft.  | 

....140 

ft.  [ 

......40 

ft.  1 

13 

ft.  | 

4 

ft.  J 

43-|- 

ft.  } 

...400.6 

ft. 

J-  Columbia. 
\ Lafayette. 


[•  Lagrange. 


[ Flatwoods. 


Fig. 


9. — Section  of  Holly 
.Springs  Well 


From  observations  of  the  geological  con- 
ditions in  the  vicinity  of  Holly  Springs  it  is  my 
belief  that  the  first  member  of  the  series  repre- 
sented in  this  well  belongs  to  the  Columbia;  that 
the  second  member  belongs  to  the  Lafayette; 
that  the  members  from  3 to  9 inclusive  belong 
to  the  Lagrange  and  that  member  10  belongs  to 
the  Flatwoods. 

According  to  McGee*  Johnson  assigns  a thick- 
ness of  200  feet  to  the  Lafayette  at  Holly  Springs. 
It  is  my  present  belief  that  one-half  of  that 
amount  would  include  the  maximum  thickness  of 
the  Lafayetteat  Holly  Springs. 

*See  U.  S.  G.  S.  12th  Annual  Report,  p.  Jfi8. 


Clay  No.  16. 

On  the  Butler  Hern  place  two  miles  west  of  Holly 
Springs  the  following  geological  section  is  exposed  in  a 
small  cusp  of  a crenulated  gulch  which  are  so  common  in 
the  region. 

1.  Brown  loam  (Columbia)  4 feet. 

2.  Reddish  sand  3 feet. 

3.  Clay  with  a reddish  tinge  4 feet. 

4.  Grayish-yellow  clay  with  some  sand  5 feet. 

Light  yellow  to  white  clay 5 feet. 

The  clay  in  this  outcrop  is  laminated  and  contains 
thin  layers  of  sand  and  sandy  clay  in  the  upper  part.  The 
first  member  of  the  section  belongs  to  the  Columbia.  - section, 
Members  2 and  3 probably  to  the  Lafayette  though  the  Holering™" 


MISSISSIPPI  A.  & M.  COLLEGE 


47 


separation  is  not  distinctly  marked.  Members  4 and  5 are,  for 
stratigraphical  reasons,  placed  in  the  Lagrange. 

The  sample  of  clay  studied  was  taken  from  the  lowermost  stratum. 
It  is  a yellowish  plastic  clay  of  good  stoneware  quality.  Its  specific 
gravity  is  2.54.  In  water  it  slacks  readily  to  a fine  grain  and  shrinks 
in  air  drying  8 per  cent.  The  average  tensile  strength  of  its  air-dried 
briquettes  is  109  pounds  and  the  maximum  strength  is  121  pounds 
per  square  inch.  The  amount  of  water  required  to  render  it  plastic 
is  25  per  cent. 

The  chemical  composition  of  the  clay  is: 

ULTIMATE  ANALYSIS. 


Moisture 1.84 

Loss  on  Ignition  8.23 

Silica  60.78 

Ferric  Oxide  3.52 

Alumina 24.12 

Lime 73 

Magnesia  38 

Sulphur  Trioxide  38 

RATIONAL  ANALYSIS. 

Clay  Base  61.12 

Free  Silica  23.28 

Fluxers 4.63 


This  is  a good  quality  of  stoneware  clay,  the  ware  when  burned 
having  a good  strong  body,  drying  and  burning  readily.  It  could  with- 
out doubt  be  used  with  success  in  the  manufacture  of  a general  line  of 
stoneware. 

Clay  No.  17. 

On  the  old  Hern  farm,  one  and  one-half  miles  west  of  Holly  Springs 
there  is  an  old  clay  pit  formerly  worked  by  the  Holly  Springs  Stone- 
ware Co.  At  this  point  four  or  five  feet  of  white  clay  with  yellow  and 
pink  streaks  is  exposed.  Above  the  clay  there  is  a bed  of  red  sand 
(Lafayette).  Higher  up  on  the  ridge  the  Columbia  appears.  In  a 
deep  cut  at  the  side  of  the  road  near  this  point  30  or  40  feet  of  the 
red  Lafayette  sands  are  revealed.  The  clay  at  the  base  of  the  sand  is 
Lagrange. 

This  clay  possesses  the  following  properties:  It  has  a specific 
gravity  of  2.50.  In  water  it  slacks  readily  to  medium  flakes.  The 
average  tensile  strength  is  68  pounds  and  the  maximum  is  75  pounds 
per  square  inch.  In  air  drying  it  shrinks  5 per  cent.  It  requires 
25  per  cent,  of  water  to  render  it  plastic.  The  fire-shrinkage  is  about 
2 per  cent. 

When  burned  it  becomes  white,  dense  and  hard.  It  has  the  proper 
degree  of  plasticity  for  easy  moulding. 


48 


CLAYS  OF  MISSISSIPPI 


Clay  No.  18. 

In  a small  draw  on  the  W.  J.  Ray  farm,  one-half  mile  west  of  Holly 
Springs  there  is  an  outcrop  of  white  clay.  The  thickness  of  the  bed, 
as  it  is  exposed,  is  6 or  8 feet.  Judging  from  its  position  it  belongs 
to  No.  4 of  the  Holly  Springs  well  (see  record  p.  46).  An  examination 
of  the  physical  properties  of  the  clay  reveals  a specific  gravity  of  2.53. 

The  average  tensile  strength  of  the  briquettes  is  65  pounds  per 
square  inch.  The  amount  of  water  required  to  make  the  clay  plastic 
is  25  per  cent,  of  the  amount  of  clay  used.  When  dried  in  the  air  the 
clay  shrinks  6 per  cent.  The  fire-shrinkage  is  1 per  cent.  The  clay 
burns  to  a dense  white  body. 


Clay  No.  19. 


In  the  new  pit  opened  by  the  Holly  Springs  Stoneware  Company 
there  is  a stratum  of  white  or  cream  colored  clay  which  has  a thickness 
of  about  eight  feet.  This  pit  is  one  and  one-fourth  miles  east  of  Holly 
Springs. 

The  clay  is  fossil-leaf  bearing  and  laminated.  It  doubtless  be- 
longs to  the  Lagrange-Lignitic.  Overlying  the  clay  is  a bed  of  reddish 
sand  (Lafayette).  Higher  up  on  the  slope  above  the  bed  of  the  small 
run  in  which  the  clay  outcrops,  the  brown  loam  of  the  Columbia  appears. 

The  Holly  Springs  Stoneware  Company  used  this  clay  in  the  man- 
ufacture of  a general  line  of  stoneware.  The  articles  manufactured 
include  jugs,  jars,  crocks,  churns,  pitchers,  bowls,  and  flower  pots. 

The  clay  is  mixed  in  a chaser  or  wet  pan.  The  plant  is  run  by 
steam  power  and  the  clay  vessels  dried  by  steam  heat.  The  vessels 
are  burned  in  two  circular  down-draught  kilns  of  the  bee  hive  type. 
Coal  is  used  as  fuel.  The  clay  vitrifies  between  cones  5 and  6. 

Both  a white  and  a brown  glaze  is  used.  The  white  glaze  is  pro- 
duced by  a mixture  containing  feldspar  and  whiting.  The  brown 
glaze  is  produced  by  using  the  Albany  slip  clay.  A very  attractive 
vessel  is  made  by  using  the  white  glaze  for  the  body  of  the  ware  and  the 
brown  for  the  top  or  rim. 

The  capacity  of  this  plant  is  500,000  gallons  per  year. 

A chemical  analysis  of  a sample  of  clay  from  this  pit  gave  the 
following  results: 


ULTIMATE  ANALYSIS. 

Moisture 

Loss  on  Ignition  

Silica  

Ferric  Oxide  

Alumina  . 

Lime  

Magnesia  

Sulphur  Trioxide  


.94 

6.64 

67.70 

3.04 

19.69 

1.06 

.58 

.19 


MISSISSIPPI  A.  & M.  COLLEGE 


49 


Clay  Pit  of  the  Holly  Springs  Stoneware  and  Fire  Brick  Co.,  near  Holly  Springs. 


50 


CLAYS  OF  MISSISSIPPI 


RATIONAL  ANALYSIS. 


Clay  Base  49.90 

Free  Silica  37.49 

Fluxing  Impurities 4.68 


This  bed  of  clay  varies  in  the  amount  of  sandy  matter  both  ver- 
tically and  horizontally.  Averaging  the  above  analysis  with  that  of 
a sample  taken  a few  rods  away  the  following  results  are  obtained: 


Moisture 1 .23 

Loss  on  Ignition  7.35 

Silica  64.69 

Ferric  Oxide  2.54 

Alumina  22.30 

Lime  70 

Magnesia  70 

Sulphur  Trioxide  20 


In  order  to  compare  this  clay  with  other  stoneware  clays  now  in 
use  we  will  take  the  rational  analysis  obtained  from  the  above  analysis 
and  compare  it  with  the  average  rational  analyses  of  ten  clays  given  by 
Hopkins:* 


HOLLY  SPRINGS 

PENNSYLVAN- 

CLAY. 

IA  CLAY. 

Clay  Base  

56.51 

56.65 

Free  Silica  

30.48 

37.45 

Fluxing  matter 

3.94 

4.44 

Moisture  

1.23 

1.57 

Total  Silica  

64.69 

65.00 

This  comparison  shows  that  chemically  the  Holly  Springs  clay  is 
a good  stoneware  clay  as  it  it  varies  only  slightly,  and  not  at  all  in  a 
detrimental  way  from  the  average  analysis  of  these  ten  stoneware  clays. 

The  color  of  this  clay  in  the  powdered  form  varies  from  white  to 
cream.  It  has  a specific  gravity  of  2.53.  In  water  it  slacks  with  mod- 
erate rapidity  to  a fine  grain.  The  average  tensile  strength  of  its  air 
dried  briquettes  is  58  pounds,  the  maximum  is  62  pounds  per  square 
inch.  It  requires  about  30  per  cent,  of  water  to  make  it  plastic.  The 
amount  of  air-shrinkage  is  7 per  cent. 

Another  sample  collected  from  a near-by  outcrop  has  a specific 
gravity  of  2.58;  an  air  shrinkage  of  7 per  cent.;  an  average  tensile 
strength  of  59  pounds  per  square  inch;  slacks  slowly  to  fine  flakes  and 
requires  33  per  cent,  of  water  to  render  plastic. 

Clay  No.  20. 

The  Allison  Stoneware  Company  of  Holly  Springs  have  a clay 
pit  a few  rods  north  of  the  outcrop  of  No.  19.  The  clay  used  by  this 
company  is  found  under  the  following  stratigraphical  conditions: 


1 . Brown  loam  (Columbia')  2 feet. 

2.  Orange  to  red  sand  (Lafayette)  4 feet. 

3.  Laminated  cream  colored  clay  12  feet. 

4.  Variegated  sands  5 feet. 


* See  Clays  and  Clay  Inadustries  of  Pa.,  page  19 


MISSISSIPPI  A.  & M.  COLLEGE 


51 


Fig.  12. — The  Allison  Clay  Pit,  near  Holly  Springs, [“Miss, 


CLAYS  OF  MISSISSIPPI 


About  one  hundred  yards  north  of  this  outcrop  No.  2 of  the  section 
has  a thickness  of  ten  feet,  while  No.  1 attains  a thickness  of  four  feet. 
At  a higher  level  and  farther  back  from  the  creek  the  thickness  of 
both  of  these  beds  increases  greatly. 

The  sands  of  No.  4 are  cross  bedded  and  vary  much  in  color,  the 
prevailing  colors  are  red,  yellow,  purple  and  white.  But  no  deep 
orange  like  that  of  No.  2.  In  the  upper  part  are  thin  layers  of  iron- 
stone separating  thin  layers  of  clay. 

The  upper  part  of  stratum  No.  3 varies  in  color  from  white  to 
yellow  and  is  somewhat  sandy. 

In  a gulch  one  hundred  yards  north  of  this  outcrop  are  some  fine 
springs  of  clear  sparkling  water.  These  are  formed  at  the  line  of  con- 
tact between  No.  2 and  No.  3. 


The  following  is  the  chemical  composition  of  the 
Allison  clay: 


ULTIMATE  ANALYSIS. 


Moisture  1.51 

Loss  on  Ignition  8.07 

Silica  61.69 

Ferric  Oxide  2.04 

Alumina  . 24.91 

Lime  34 

Magnesia  83 

Sulphur  Trioxide  20 


RATIONAL  ANALYSIS. 


Clay  Base  63.13 

Free  Silica  23.47 

Fluxing  Impurities 3.21 


Fig.  13.  Section  at 
Allison  Clay  Pit, 
Holly  .Springs, 


The  physical  properties  of  this  clay  are:  Specific  gravity,  2.57 
to  2.58;  average  tensile  strength  of  the  briquettes,  113  pounds;  maxi- 
mum strength,  128  pounds  per  square  inch;  air-shrinkage,  8 per  cent. 
The  amount  of  water  required  for  plasticity  is  32  per  cent.  In  water 
the  clay  slacks  to  medium  fine  grains. 

Another  sample  of  clay  from  a different  part  of  the  pit  gave  a 
specific  gravity  of  2.38;  is  medium  grained;  has  an  air-shrinkage  of 
7 per  cent.;  is  white  to  light  yellow  in  color  and  requires  30  per  cent, 
of  water  to  render  it  plastic. 

The  Allison  pottery  manufactures  a general  line  of  stoneware. 
They  have  one  circular  brick  kiln  having  a capacity  of  2,500  gallons. 
A brick  oven  drier  is  used  for  drying  the  vessels.  After  remaining  on 
the  drier  for  24  hours  they  are  placed  in  the  kiln.  It  requires  about 
thirty-six  hours  to  burn  a kiln. 


MISSISSIPPI  A.  & M.  COLLEGE 


53 


Fig.  14. — The  Allison  Pottery,  Holly  Springs,  Miss. 


54 


CLAYS  OF  MISSISSIPPI 


Clay  No.  21. 

At  the  southern  boundary  of  the  cemetery  in  Holly  Springs  a 
white  or  yellowish  white  clay  underlies  a deposit  of  reddish  sand.  There 
are  several  thin  layers  of  clay  separated  by  thin  beds  of  sand.  The 
geological  position  of  the  clay  is  not  clear  but  it  is  probably  Lafayette. 
As  much  as  forty  feet  of  Lafayette  is  exposed  in  a gulch  at  the  north- 
eastern corner  of  the  cemetery.  The  greater  part  of  the  outcrop  is 
red  sand  or  sandy  clay  but  toward  the  bottom  of  the  outcrop  are  some 
thin  layers  of  white  clay.  Doubtless  they  mark  the  beginning  of  the 
transition  to  the  Lagrange.  This  forty-foot  stratum  belongs  to  the 
same  geological  horizon  as  the  stratum  No.  2 of  the  Holly  Springs  well. 
(See  page  46.) 

The  clay  of  the  first  named  locality  is  very  plastic  and  when  placed 
in  water  slacks  to  medium-sized  flakes.  The  air  dried  briquettes  have 
an  average  tensile  strength  of  46  pounds  and  a maximum  strength  of 
49  pounds  per  square  inch.  The  specific  gravity  ranges  from  2.20  to 
2.36. 

It  requires  about  one-fifth  of  its  weight  of  water  to  render  it  plastic. 
In  air  drying  it  shrinks  6 per  cent.  It  vitrifies  at  cone  5,  forming  a 
strong  dense  body. 

Clay  No.  22. 

In  the  public  road  about  one-half  of  a mile  south  of  Holly  Springs 
there  is  an  outcrop  of  cream  colored  clay.  This  clay  occurs  under 
much  the  same  conditions  as  No.  21.  It  is  near  the  line  of  contact  of 
Lafayette  and  the  Lagrange. 

The  specific  gravity  of  the  clay  is  2.47.  It  slacks  rapidly  to 
medium  grain.  Its  average  tensile  strength  is  51  pounds  per  square 
inch. 

The  amount  of  water  required  for  mixing  the  clay  is  25  per  cent. 
It  shrinks  in  air  drying  4 per  cent.  It  burns  to  a strong  white  body 
and  is  a good  potter’s  clay. 

Clay  No.  23. 

This  clay  occurs  on  the  public  road  one  mile  south  of  Holly  Springs. 
The  following  section  is  exposed: 


1.  Brown  loam  (Columbia)  6 ft. 

2.  White  clay.. 6 ft. 

3.  Sands,  dark  red  to  purple  4 ft. 

4.  Sandstone,  red  to  purple,  ferruginous 8 in. 

5.  Loose  sand  and  small  gravel  1 ft. 

6.  Ferruginous  sand  stone  6 in. 


MISSISSIPPI  A.  & M.  COLLEGE 


55 


In  another  outcrop  on  the  east  side  of  the  road  No.  2 is  covered 
with  ten  feet  of  reddish  sand  (Lafayette).  Members  of  this  section 
from  2 to  6 inclusive  belong  to  the  Lagrange. 

The  layers  of  sandstone  are  very  irregular  in  thickness  and  are 
not  continuous  for  great  distances.  The  wine-colored  to  purple  sands 
of  No.  5 contain  many  irregular  ironstone  concretions. 

Owing  to  the  bad-land  type  of  topography  the  clay  outcrops  are 
numerous  in  this  region.  Deep  gulches  with  crenulate  margins  have 
been  carved  not  alone  in  the  Columbia  and  the  Lafayette  formations 
but  also  in  the  sub-formational  Lagrange. 

The  white  clay  of  No.  2 is  plastic  and  has  a specific  gravity  of 
2.50  (average).  The  average  tensile  strength  is  40  pounds  per  square 
inch.  It  requires  about  32  per  cent,  of  water  to  render  the  clay  plastic. 
Its  air-shrinkage  is  6 per  cent. 

It  vitrifies  at  cone  6,  forming  a dense  white  body. 

Clay  No.  24. 

This  is  a white  clay  similar  to  the  last  occurring  near  the  colored 
school  building  in  Holly  Springs. 

The  average  specific  gravity  is  2.40.  The  tensile  strength  of  the 
air  dried  briquettes  is  45  pounds  per  square  inch.  The  amount  of 
water  required  for  plasticity  is  25  per  cent,  of  the  weight  of  the  clay. 

The  air  shrinkage,  measured  on  the  briquettes,  is  8 per  cent. 

Clay  No.  25. 

Near  the  Frisco  Station  in  Holly  Springs  there  is  an  outcrop  of 
white  fire  clay  of  the  plastic  variety.  Four  or  five  feet  of  the  clay 
is  exposed.  It  is  succeeded  above  by  a yellowish  loam  passing  to 
brown  at  the  top  and  having  a thickness  of  about  five  feet. 

The  clay  contains  a high  per  cent,  of  silica  and  a low  per  cent,  of 
fluxing  impurities.  It  can  be  moulded  without  difficulty  and  dries 
without  cracking  or  checking. 

A chemical  analysis  of  the  clay  gave  the  following  results: 


ULTIMATE  ANALYSIS. 

Moisture  87 

Loss  on  Ignition  1.93 

Silica  88.52 

Ferric  Oxide  1 .64 

Alumina 5.26 

Lime 73 

Magnesia  13 

Sulphur  Trioxide  43 

RATIONAL  ANALYSIS. 

Olay  Base  13.33 

Free  Silica  80.45 

Fluxing  Impurities 2.50 


56 


CLAYS  OF  MISSISSIPPI 


The  specific  gravity  ranges  from  2.56  to  2.75.  Its  average  tensile 
strength  is  95  pounds  per  square  inch.  Upon  drying  in  the  air  it 
shrinks  2 per  cent.  The  amount  of  water  required  to  render  it  plastic 
is  15  per  cent. 

When  burnt  the  clay  has  a cream  or  flesh  tint  and  a firm  compact 
body.  This  clay  remains  unfused  at  the  temperature  required  to  fuse 
cone  No.  20. 

Clay  No.  26. 

This  clay  is  from  an  outcrop  east  of  the  Illinois  Central  Station 
in  Holly  Springs.  It  is  from  the  same  geological  horizon  as  No.  25. 

It  is  a white  highly  refractory  clay  containing  large  grains  of  pure 
clear  quartz.  Many  of  the  quartz  grains  are  as  large  as  grains  of  wheat. 
It  has  an  average  specific  gravity  of  2.63.  The  average  tensile  strength 
of  its  air-dried  briquettes  is  102  pounds  per  square  inch.  It  requires 
* about  14  per  cent,  of  water  to  render  it  plastic.  It  may  be  moulded 
readily  into  bricks  which  do  not  crack  on  drying. 

It  burns  to  a slightly  pink  color  which  disappears  before  vitrifica- 
tion leaving  the  burnt  clay  white  or  cream  colored. 

The  chemical  analysis  of  a sample  of  clay  taken  from  this  horizon 
gave  the  following  results: 


ULTIMATE  ANALYSIS. 

Moisture 1.23 

Loss  on  Ignition  2.41 

Silica  66.66 

Ferric  Oxide  1.57 

Alumina  22.29 

Lime  , 62 

Magnesia  28 

Sulphur  Trioxide  1 1 

RATIONAL  ANALYSIS. 

Clay  Base  . 56.49 

Free  Silica  32.46 

Fluxing  Impurities 4 83 


This  clay  remained  unfused  at  the  point  of  fusion  of  cone  No.  20. 
Clay  No.  27. 

This  clay  was  collected  from  near  the  brick  yard  at  Holly  Springs. 
It  is  a light  cream  colored  clay.  The  specific  gravity  of  one  sample 
is  2.30.  In  water  it  slacks  readily  to  fine  flakes.  The  air-shrinkage 
is  8 per  cent. 

The  chemical  composition  of  this  clay  is  as  follows: 

ULTIMATE  ANALYSIS. 


Moisture  96 

Loss  on  Ignition  6.70 

Silica  67.02 

Ferric  Oxide  . 2.93 


MISSISSIPPI  A.  & M.  COLLEGE 


57 


Alumina 20.89 

Lime 67 

Magnesia  55 

Sulphur  Trioxide  __ 49 

RATIONAL  ANALYSIS. 

Clay  Base  52.95 

Free  Silica  34.96 

Fluxing  Impurities 4.15 


It  may  be  classed  as  a stoneware  clay  of  good  quality. 

Clay  No.  28. 

A yellowish  white  plastic  clay  from  the  farm  of  J.  Dunlap,  four 
miles  southeast  of  Holly  Springs.  The  outcrop  is  near  the  Frisco 
railroad.  The  chemical  properties  of  the  clay  are: 


ULTIMATE  ANALYSIS. 

Moisture  66 

Loss  on  Ignition  ^ 7.25 

Silica  62.41 

Ferric  Oxide  2.80 

Alumina  .. 24.02 

Lime  57 

Magnesia  50 

Sulphur  Tri oxide  .. 56 

RATIONAL  ANALYSIS. 

Clay  Base  60.87 

Free  Silica  25.56 

Fluxing  Impurities 3.87 


The  average  specific  gravity  of  the  clay  is  2.48.  The  air-shrinkage 
is  4 per  cent.  May  be  classed  as  an  excellent  stoneware  clay. 

Clay  No.  29. 

This  is  a white  clay  from  the  Ballard  place  at  Holly  Springs. 
It  has  a specific  gravity  of  2.37.  It  slacks  readily  in  water  to  fine  grain. 
On  drying  in  the  air  it  shrinks  8 per  cent. 

The  following  is  the  chemical  composition  of  a sample  of  this  clay: 

ULTIMATE  ANALYSIS. 


Moisture. 1.74 

Loss  on  Ignition  7.39 

Silica  63.95 

Ferric  Oxide  3.88 

Alumina  21.42 

Lime 39 

Magnesia  73 

Sulphur  Trioxide  29 


RATIONAL  ANALYSIS. 


Clay  Base  54.28 

Free  Silica  31.09 

Fluxing  Impurities 5.00 


This  is  a potters  clay  of  good  quality.  It  may  be  molded  readily 
and  dries  and  burns  without  checking. 


58 


CLAYS  OF  MISSISSIPPI 


Clay  No.  30. 

North  of  Mahon  on  the  E.  T.  Fant  farm  there  is  an  outcrop  of 
pinkish-to-white  clay.  This  is  a plastic  clay  exhibiting  many  mus- 
covite crystals  which  are  visible  to  the  unaided  eye. 

The  amount  of  water  required  to  render  it  plastic  is  about  32  per 
cent.  The  air-shrinkage  is  five  per  cent.  The  specific  gravity  of  one 
sample  was  2.25. 

A sample  of  yellow  clay  from  the  same  locality  is  plastic;  has  a 
specific  gravity  of  2.24;  an  air-shrinkage  of  6 per  cent,  and  a tensile 
strength  of  45  pounds  per  square  inch. 

A sample  of  cream  colored  clay  from  the  same  place  has  a specific 
gravity  of  2.40.  It  is  plastic  and  shrinks  in  air  drying  4 per  cent. 

A sample  of  the  pinkish  clay  has  the  following  chemical  com- 
position: 

ULTIMATE  ANALYSIS. 

Moisture 83 

Loss  on  Ignition  6.12 

Silica  70.86 

Ferric  Oxide  4.50 

Alumina 15.68 

Lime  45 

Magnesia  79 

Sulphur  Trioxide  29 

RATIONAL  ANALYSIS. 

Clay  Base  39.74 

Free  Silica  46.80 

Fluxing  Impurities 5.74 

Clay  No.  31. 

Occurs  on  the  farm  of  Home  Terr  west  of  Hudsonville.  It  is  a 
yellow,  or  in  places,  light  cream  colored  clay. 

The  chemical  composition  is: 

ULTIMATE  ANALYSIS. 

Moisture 1.92 

Loss  on  Ignition  7.66 

Silica  63.56 

Ferric  Oxide  2.83 

Alumina  21.92 

Lime  48 

Magnesia  62 

Sulphur  Trioxide  28 

RATIONAL  ANALYSIS. 

Clay  Base 55.55 

Free  Silica  29.93 

Fluxing  Impurities 93 

The  specific  gravity  of  the  clay  is  2.26.  It  is  rendered  plastic 
by  mixing  witli  30  per  cent,  of  water.  The  air  shrinkage  is  8 per  cent. 
A good  quality  of  stoneware  clay. 


MISSISSIPPI  A.  & M.  COLLEGE 


59 


Clay  No.  32. 

Near  the  Illinois  Central  Railroad,  two  miles  south  of  Holly  Springs 
there  is  an  outcrop  of  white  plastic  clay  which  has  the  following  chem- 
ical composition: 

ULTIMATE  ANALYSIS. 


Moisture  74 

Loss  on  Ignition  5.36 

Silica  84.40 

Ferric  Oxide  1.30 

Alumina 6.79 

Lime 85 

Magnesia  27 

Sulphur  Trioxide  17 

RATIONAL  ANALYSIS. 

Clay  Base  17.21 

Free  Silica  73.98 

Fluxing  Impurities 2.43 


The  specific  gravity  of  the  clay  is  2.47.  The  air-shrinkage  is 
4 per  cent. 

Clay  No.  33. 

A cream  colored  clay  from  the  Marshall  county  poor  farm.  It 
is  plastic;  slacks  readily  in  water;  and  has  a specific  gravity  of  2.17. 
The  air-shrinkage  is  6 per  cent. 

The  chemical  composition  of  a sample  of  this  clay  is: 


ULTIMATE  ANALYSIS. 

Moisture.. 1.78 

Loss  on  Ignition  8.11 

Silica  61.31 

Ferric  Oxide  2.77 

Alumina 24.44 

Lime 57 

Magnesia  29 

Sulphur  Trioxide  23 

RATIONAL  ANALYSIS. 

Clay  Base  61.94 

Free  Silica  23.81 

Fluxing  Impurities 3.63 


This  is  a potter’s  clay  of  good  quality. 

Clay  No.  34. 

Is  from  the  railroad  cut  south  of  the  Mahon  station.  It  is  a salmon 
colored  clay  having  a specific  gravity  of  2.51.  It  is  gritty  to  the  taste 
and  contains  macroscopic  muscovite  crystals. 

The  chemical  properties  of  the  clay  are: 

ULTIMATE  ANALYSIS. 


Moisture 44 

Loss  on  Ignition  4.75 

Silica  77.64 


Fig.  15 — A Brick  Machine  of  the  Stiff-Mud  Type. 


MISSISSIPPI  A.  & M.  COLLEGE  61 

Ferric  Oxide  3.10 

Alumina 12.33 

Lime 51 

Magnesia  12 

Sulphur  Trioxide  54 

RATIONAL  ANALYSIS. 

Clay  Base  31.25 

Free  Silica  58.72 

Fluxing  Impurities 3.73 


Clay  No.  35. 

This  clay  occurs  on  a farm  owned  by  Rand  and  Norfleet,  north- 
west of  Holly  Springs.  It  is  a white  plastic  clay  having  the  following 
chemical  composition: 

ULTIMATE  ANALYSIS. 


Moisture  1.23 

Loss  on  Ignition  7.02 

Silica  65.88 

Ferric  Oxide  2.89 

Alumina  21.19 

Lime 72 

Magnesia  15 

Sulphur  Trioxide  30 

RATIONAL  ANALYSIS. 

Clay  Base  53.70 

Free  Silica  33.47 

Fluxing  Impurities 3.76 


The  specific  gravity  of  the  clay  is  2.31.  The  air-dried  briquettes 
shrink  8 per  cent.  A good  grade  of  potter’s  clay. 

Clay  No.  36. 

A white  fire  claj7  from  the  Jones  place  just  east  of  the  corporation 
limits,  Holly  Springs.  The  clay  contains  a large  number  of  visible 
quartz  grains.  It  is  plastic  and  has  a specific  gravity  of  2.67.  The 
air  dried  briquettes  shrink  6 per  cent.  Unfused  at  fusion  point  of 
cone  No.  19.  Probably  will  stand  much  higher  temperature. 

Benton  County. 

Geology. — Benton  County  occupies  the  northeastern  portion  of 
the  Lignitic  area  of  Mississippi.  The  sub-formation  of  the  county  is 
the  Lignitic-Eocene  comprising  the  Flatwoods  clay  and  the  Lagrange 
sands  and  clays.  The  former  occupies  the  eastern  part  of  the  county 
and  the  latter  the  western. 

The  surficial  formations  of  the  county  are  the  Lafayette  and  the 
Columbia,  The  stratigraphical  relations  of  these  formations  are  ex- 
hibited in  cuts  along  the  Illinois  Central  railroad: 


62 


CLAYS  OF  MISSISSIPPI 


Clays. — The  clay  industry  of  Benton  county  is  undeveloped.  The 
county  possesses  some  excellent  stoneware  clays.  The  following  is  an 
average  of  the  analyses  of  three  of  its  stoneware  clays: 


ULTIMATE  ANALYSIS. 

Moisture 88 

Loss  on  Ignition  8.09 

Silica  60.07 

Ferric  Oxide  3.35 

Alumina 25.01 

Lime 54 

Magnesia  34 

Sulphur  Trioxide  25 

RATIONAL  [ANALYSIS. 

Clay  Base  63.42 

Free  Silica  21.67 

Fluxing  Impurities 4.22 


Comparing  the  rational  analysis  with  that  of  the  ten  foreign  stone- 
ware clays  given  on  page  17,  we  obtain  the  following  results: 

BENTON  COUNTY.  FOREIGN. 

Clay  Base  63.43  56.65 

Free  Silica  21,67  37.45 

Fluxing  Matter  4.22  4.44 

Moisture .88  1.57 

Total  Silica 60.07  65.00 

This  comparison  shows  a higher  clay  base  and  less  fluxing  impuri- 
ties for  the  Benton  county  clays. 

Clay  No.  37. 

On  the  J.  Maclin  farm  southwest  of  Spring  Hill  in  Benton  county 
is  a deposit  of  white  plastic  clay.  The  clay  contains  muscovite  crystals 
of  macroscopic  size.  It  is  distinctly  gritty  to  the  taste.  In  water 
it  slacks  readily  to  a fine  grain.  The  specific  gravity  is  2.55.  In  air 
drying  it  shrinks  4 per  cent. 

A sample  of  the  clay  has  the  following  composition: 

ULTIMATE  ANALYSIS. 


Moisture 62 

Loss  on  Ignition  7.02 

Silica  64.88 

Ferric  Oxide  4.19 

Alumina 20.70 

Lime 69 

Magnesia  59 

Sulphur  Trioxide  Trace. 

RATIONAL  ANALYSIS. 

Clay  Base  52.46 

Free  Silica 33.10 

Fluxing  Impurities  5.47 


This  clay  and  the  four  following  clays  may  be  classed  as  good" 
potter’s  clays.  It  is  possible  that  some  of  them  may  be  refractory 


MISSISSIPPI  A.  & M.  COLLEGE  63 

enough  to  be  classed  as  fire  clays  since  in  a preliminary  test  two  were 
not  fused  at  the  fusion  point  of  Seger  cone  No.  20. 


Clay  No.  38. 


A pink  clay  from  the  J.  T.  Brown  farm  south  of  Spring  Hill.  It 
is  a plastic  clay  having  a specific  gravity  ranging  from  2.04  to  2.24. 
The  air  shrinkage  of  its  briquettes  is  8 per  cent. 

The  chemical  composition  of  the  clay  is: 

ULTIMATE  ANALYSIS. 


Moisture.. 1.12 

Loss  on  Ignition  9.22 

Silica  55.87 

Ferric  Oxide  2.44 

Alumina  30.19 

Lime  53 

Magnesia  24 

Sulphur  Trioxide  23 


RATIONAL  ANALYSIS. 


Clay  Base  76.51 

Free  Silica  9.55 

Fluxing  Impurities 3.21 


This  clay  was  unfused  at  the  temperature  required  to  fuse  cone 
No.  20. 


Clay  No.  39. 


This  is  a yellow  plastic  clay  from  the  Umbarger  farm  five  miles 
east  of  Canaan.  The  clay  has  the  following  chemical  properties: 

ULTIMATE  ANALYSIS. 


Moisture  23 

Loss  on  Ignition  4.81 

Silica  75.78 

Ferric  Oxide  3.56 

Alumina 14.11 

Lime 54 

Magnesia  52 

Sulphur  Trioxide  00.00 

RATIONAL  ANALYSIS. 

Clay  Base  37.56 

Free  Silica  54.13 

Fluxing  Impurities 4.62 


The  clay  is  gritty  to  the  taste  and  contains  visible  crystals  of 
muscovite.  The  specific  gravity  is  2.35.  The  air  dried  briquettes 
shrink  4 per  cent. 

Clay  No.  40. 


On  the  W.  P.  Bonton  farm  five  miles  northeast  of  Canaan  there 
is  an  outcrop  of  pinkish-white  clay.  In  water  the  clay  slacks  with  mod- 


64 


CLAYS  OF  MISSISSIPPI 


erate  rapidity  to  a fine  grain.  The  specific  gravity  is  2.23.  The  air- 
shrinkage  is  4 per  cent. 

A chemical  analysis  of  a sample  of  the  clay  gave  the  following  result: 


ULTIMATE  ANALYSIS. 

Moisture  98 

Loss  on  Ignition  8.69 

Silica  56.62 

Ferric  Oxide  2.60 

Alumina  28.60 

Lime 45 

Magnesia  20 

Sulphur  Trioxide  32 

RATIONAL  ANALYSIS. 

Clay  Base  72.48 

Free  Silica  12.44 

Fluxing  Impurities 3.25 


Clay  No.  41. 

A clay  varying  in  color  from  white  to  cream  from  the  0.  Parham 
farm  southeast  of  Michigan  City.  One  sample  of  the  clay  gave  a 
specific  gravity  of  2.10. 

The  chemical  properties  of  the  clay  are  as  follows: 

ULTIMATE  ANALYSIS. 


Moisture i .09 

Loss  on  Ignition  8.37 

Silica  59.02 

Ferric  Oxide  3.25 

Alumina  25.78 

Lime 47 

Magnesia  24 

Sulphur  Trioxide  42 


RATIONAL  ANALYSIS. 


Clay  Base  65.33 

Free  Silica  19.47 

Fluxing  Impurities 3.96 


Clay  unfused  at  the  temperature  required  to  fuse  cone  No.  20. 


Lafayette  County. 

This  county,  like  its  northern  neighbor,  Marshall,  has  the  Lignitic- 
Eocene  for  its  sub-formation.  The  Lafayette  and  the  Columbia  are 
both  present  as  surficial  formations.  This  is  the  county  which  gave 
the  name  to  the  former.  These  later  formations  reach  their  maximum 
thickness  for  this  county  on  the  divide  between  the  Yocona  and  the 
Tallahatchie  rivers.  The  approaches  to  this  divide  from  the  valleys 
present  a rugged  form  of  topography.  Gulches  with  crenulate  margins, 
ridges  with  moderately  sharp  crests  and  pinnacled  forms  are  charac- 
teristic of  many  localities. 


MISSISSIPPI  A.  & M.  COLLEGE 


65 


Clay  No.  42. 

In  the  public  road  about  three  blocks  east  of  the  Oxford  Court 
House  the  following  section  is  exposed: 


1.  Brownish  loam  4 ft. 

2.  Red  and  white  sand.. 6 ft. 

3.  White  clay  with  bluish  tint 1 ft. 

4 .White  clay  with  yellow  and  pink  tints  4 ft. 


A sample  of  the  clay  from  the  last  named  stratum  on  analysis 
gave  the  following  results: 


ULTIMATE  ANALYSIS. 

Moisture 69 

Loss  on  Ignition  8.20 

Silica  .60.00 

Alumina 27.80 

Ferric  Oxide  75 

Calcium  Oxide  1.38 

Sulphur  Trioxide  20 

RATIONAL  ANALYSIS. 

Clay  Base  70.45 

Free  Silica  17.35 

Fluxing  Impurities 2.33 


The  amount  of  water  required  to  render  this  clay  plastic  is  30 
per  cent,  of  the  weight  of  the  dry  clay.  The  average  tensile  strength 
of  the  air  dried  briquettes  is  35  pounds. 

The  specific  gravity  is  2.46.  The  amount  of  shrinkage  in  air 
drying  is  6 per  cent.  The  fire-shrinkage  is  about  1 per  cent. 

The  burned  clay  is  white  in  color  and  of  firm  texture. 

Clay  No.  43. 


Is  from  a point  in  the  street  near  the  colored  school  building  in 
Oxford.  The  prevailing  colors  of  the  clay  in  the  outcrop  are  pink, 
yellow  and  white.  In  the  powdered  form  the  color  is  cream.  It 
slacks  slowly  in  water  to  a fine  flake.  The  amount  of  water  required 
for  plasticity  is  25  per  cent,  of  the  weight  of  the  clay. 

The  specific  gravity  ranges  from  2.31  to  2.56.  Air-dried  briquettes 
have  an  average  tensile  strength  of  48  pounds.  These  shrink  in  drying 
7 per  cent.  Air-shrinkage  is  about  5 per  cent. 

The  chemical  composition  of  the  clay  is: 


ULTIMATE  ANALYSIS. 

Moisture  

Loss  on  Ignition  

Silica  

Ferric  Oxide  

Alumina  . 

Lime 

Magnesia  

Sulphur  Trioxide  


1.14 
9.11 
57.79 
2.98 
26.03 
. .44 

.10 
. .24 


66 


CLAYS  OF  MISSISSIPPI 


RATIONAL  ANALYSIS. 


Clay  Base  65.97 

Free  Silica  17.85 

Fluxing  Impurities 3.52 


This  clay  burns  to  a nearly  white  body.  The  ware  becomes  firm, 
compact  and  hard  at  red  heat.  Burns  without  checking  or  cracking. 

Is  easily  moulded  into  any  desired  form  and  may  be  considered  a good 
clay  for  the  potter’s  use. 

Clay  No.  44. 


In  a small  run  on  the  Brunner  farm,  two  and  one-half  miles  north- 
east of  Oxford  the  following  section  is  exposed: 


1.  Reddish  unstratified  sand  30  ft. 

2.  Stratified  red  sand  with  white  partings 10  ft. 

3.  Laminated,  pink,  yellow  and  white  clay  4 ft. 

4.  Cross-bedded,  micaceous  sand  4 ft. 


Near  the  top  the  first  member  of  the  section  contains  ironstone 
concretions  and  the  fragments  of  irregular  layers  of  ironstone. 

A sample  of  the  clay  from  number  3 exhibited  the  following  physical 
characteristics:  slightly  gritty  to  the  taste  and  feel;  slacks  rapidly  to 
medium  grain ; requires  one-fourth  its  weight  of  water  to  render  plastic. 

The  average  tensile  strength  is  20  pounds  per  square  inch.  The 
air-shrinkage  is  2 per  cent. 

Muscovite  crystals  are  visible  to  the  naked  eye  but  pyrite  or  other 
deleterious  substances  are  not  present.  The  average  specific  gravity 
is  2.34. 

Clay  No.  45. 

A grayish  sandy  fire  clay  from  the  same  locality  as  the  preceding  has 
the  following  chemical  properties: 


ULTIMATE  ANALYSIS. 


Moisture  1.16 

Loss  on  Ignition  2.84 

Silica  70.35 

Ferric  Oxide  1.86 

Alumina  18.61 

Lime 51 

Magnesia  10 

Sulphur  Trioxide  .. 24 

RATIONAL  ANALYSIS. 

Clay  Base  47.18 

Free  Silica  41.78 

Fluxing  Impurities 2.47 


The  clay  becomes  plastic  when  mixed  with  about  16  per  cent,  of 
water.  The  specific  gravity  varies  from  2.45  to  2.64.  The  air-dried 
briquettes  have  an  average  tensile  strength  of  115  pounds  per  square 
inch.  They  shrink  in  drying  2 per  cent. 


MISSISSIPPI  A.  & M.  COLLEGE 


67 


Clay  No.  46. 

This  clay  is  on  the  Russel  farm,  one-half  mile  east  of  No.  44.  The 
outcrop  consists  of  6 feet  of  variegated  clay  covered  by  20  feet  or  more 
of  reddish  sand.  A spring  occurs  on  the  slope  of  the  hill  at  the  point 
of  contact  of  the  clay  and  sand.  The  upper  member  has  all  the  char- 
acteristics of  the  Lafayette.  The  geological  position  of  the  lower 
member  is  uncertain  but  is  probably  Lagrange. 

The  following  is  the  chemical  composition  of  a sample  of  the  clay: 


ULTIMATE  ANALYSIS. 

Moisture  1.16 

Loss  on  Ignition  10.14 

Silica  51.88 

Ferric  Oxide  3.53 

Alumina  30.64 

Lime 58 

Magnesia  .60 

RATIONAL  ANALYSIS. 

Clay  Base  77.65 

Free  Silica  4.87 

Fluxing  Impurities 4.71 


This  clay  is  noticeable  for  its  high  percentage  of  clay  substance  and 
its  low  percentage  of  sandy  matter.  It  is  very  plastic  when  mixed 
with  32  per  cent,  of  water.  White  and  pink  are  the  prevailing  colors. 

The  average  tensile  strength  is  35  pounds  per  square  inch.  Its 
specific  gravity  ranges  from  2.42  to  2.51.  In  water  it  slacks  rapidly 
to  medium  size  flakes.  The  air-shrinkage  is  5 per  cent,  and  the  fire- 
shrinkage  2 per  cent.  The  unglazed  product  of  the  kiln  is  hard  and 
firm  and  cream  in  color.  The  clay  is  unquestionably  a desirable  one 
for  stoneware  purposes. 

Clay  No.  47. 

Is  from  the  public  road  three  and  one-half  miles  northeast  of 
Oxford.  It  is  a white  clay  with  pink  or  yellow  tints  in  some  layers. 

The  physical  properties  of  the  clay  are:  Specific  gravity  ranging 
from  2.38  to  2.47;  average  tensile  strength,  55  pounds  per  square  inch. 
In  water  it  slacks  slowly  to  medium  grains.  When  mixed  with  33  per 
cent,  of  water  and  air-dried  it  shrinks  6 per  cent. 

Clay  No.  48. 

This  is  a light  brown  clay  occurring  on  the  Crouch  farm  three 
miles  northeast  of  Oxford.  The  clay  contains  many  muscovite  crystals 
of  macroscopic  size.  The  specific  gravity  is  2.48. 

The  amount  of  water  required  to  render  it  plastic  is  32  per  cent. 
The  average  tensile  strength  of  the  clay  is  53  pounds  per  square  inch. 
In  air  drying  it  shrinks  5 per  cent. 


68 


CLAYS  OF  MISSISSIPPI 


Fig.  16.  Unconformity,  near  Wiggins’  Farm. 

Clay  No.  49. 

On  the  James  Wiggin’s  farm  two  and  one-half  miles  southeast  of 
Oxford  there  is  an  outcrop  of  white  plastic  clay  which  forms  the  basal 


member  of  the  following  section: 

1.  Soil  5 ft. 

2.  Reddish  brown  sand,  Lafayette 10  ft. 

3.  Yellowish  clay  with  thin  ironstone  partings 3 ft. 

4.  White  clay 4 -|-  ft. 


There  is  a decided  unconformity  between  numbers  2 and  3 near 
this  point  (See  figure  16.)  This  unconformity  probably  marks  the 
line  of  separation  for  the  Lafayette  and  the  Lagrange. 

The  white  clay  of  number  4 is  unctious  and  only  slightly  gritty 
to  the  taste.  The  specific  gravity  ranges  from  2.26  to  2.45.  The  air 
dried  briquettes  have  an  average  tensile  strength  of  36  pounds.  The 
air-shrinkage  is  4 per  cent.  It  requires  25  per  cent,  of  water  to  make 
the  clay  plastic. 

The  chemical  composition  of  the  clay  is: 

ULTIMATE  ANALYSIS. 


• t r’r  rr  Moisture 96 

LT  Loss  on  Ignition  6.41 

- - - —i  Silica  68.20 

= r : Ferric  Oxide  1.86 

~ — -l  Alumina  17.48 

Lime 65 

Fig.  17.  Section  Magnesia  21 

at  Wiggins’  Sulphur  Trioxide  J2 

Clay  Pit.  r 

RATIONAL  ANALYSIS. 

Clay  Base  44.32 

Free  Silica  41.36 

Fluxing  Impurities 2.72 


MISSISSIPPI  A.  & M.  COLLEGE 


69 


Clay  No.  50. 

A pinkish  white  clay  from  the  Tubbs  farm  three  miles  south  of 
Oxford.  An  analysis  of  a sample  of  this  clay  gave  the  following  results : 

ULTIMATE  ANALYSIS. 


Moisture  90 

Loss  on  Ignition  8.35 

Silica  60.40 

Ferric  Oxide  1.32 

Alumina 27.68 

Lime 1.08 

Magnesia  00.00 

Sulphur  Trioxide  00.00 

RATIONAL  ANALYSIS. 

Clay  Base  70.15 

Free  Silica  17.93 

Fluxing  Impurities 2.40 


This  clay  has  a specific  gravity  of  2.44  to  2.58.  In  water  it  slacks 
readily  to  flakes  of  medium  size.  The  air  dried  briquettes  have  an 
average  tensile  strength  of  38  pounds  per  square  inch.  They  shrink 
in  air  drying  2 per  cent.  The  amount  of  water  required  to  render  the 
clay  plastic  is  one-third  of  its  weight.  To  the  taste  the  clay  is  very 
slightly  gritty.  To  the  feel  it  is  unctions. 

Clay  No.  51  . 

A yellow  to  buff  colored  clay  from  the  Wyley  farm  six 
miles  southwest  of  Oxford.  It  is  a plastic  clay  containing 
muscovite  crystals  of  mascroscopic  size. 

The  average  specific  gravity  is  2.24.  The  air-shrinkage 
of  briquettes  made  from  finely  ground  clay  is  4 per  cent. 

on  Tubbs’  The  following  is  the  chemical  composition: 

Farm. 

ULTIMATE  ANALYSIS. 


Moisture 1 .64 

Loss  on  Ignition  8.99 

Silica  57.48 

Ferric  Oxide  2.43 

Alumina 26.94 

Lime 78 

Magnesia  27 

Sulphur  Trioxide  20 

RATIONAL  ANALYSIS. 

Clay  Base  68.27 

Free  Silica  16.15 

Fluxing  Impurities 3.48 


Another  clay  from  the  same  locality  is  light  yellow  to  white  in 
color.  It  has  a specific  gravity  of  2.30.  ' Slacks  readily  in  water  to 


70 


CLAYS  OF  MISSISSIPPI 


fine  grain.  The  average  tensile  strength  is  35  pounds  per  square  inch. 
The  air  shrinkage  is  5 per  cent. 

A clay  similar  to  the  above  occurs  on  the  Sisk  farm  three  miles 
southeast  of  Oxford  (Sec.  10,  T.  9,  R,  3,  West). 

Some  of  its  physical  characters  are  as  follows:  The  specific  grav- 
ity is  2.59.  It  becomes  plastic  when  mixed  with  25  per  cent  of  water. 
The  average  tensile  strength  is  45  pounds  per  square  inch. 

The  air  dried  briquettes  shrink  6 per  cent.  Pale  pink  and  white 
are  the  prevailing  colors. 

Clay  No.  52. 

An  outcrop  of  white  clay  is  found  on  the  Callicott  farm  in  the  next 
section  south  of  the  one  above  mentioned. 

This  clay  has  the  following  chemical  composition: 

ULTIMATE  ANALYSIS. 


Moisture 90 

Loss  on  Ignition  6.17 

Silica  68.75 

Ferric  Oxide  1.68 

Alumina 19.57 

Lime 56 

Magnesia  19 

Sulphur  Trioxide  13 

RATIONAL  ANALYSIS. 

Clay  Base  49.59 

Free  Silica  38.73 

Fluxing  Impurities 2.43 


The  physical  properties  of  the  clay  are:  Specific  gravity,  2.17; 
air  shrinkage,  4 per  cent.;  average  tensile  strength,  30  pounds  per 
square  inch.  The  amount  of  water  required  is  25  per  cent  of  the  weight 
of  the  clay. 

Another  sample  of  clay  taken  from  the  same  locality  is  of  a pinkish 
white  color.  It  has  a specific  gravity  of  2.57.  The  average  tensile 
strength  is  45  pounds  per  square  inch.  Its  air-shrinkage  is  5 per  cent. 

On  the  next  section  west  is  a white  clay  having  a specific  gravity 
of  2.53.  It  is  plastic  when  mixed  with  one-fourth  its  weight  of  water. 
It  shrinks  4 per  cent,  in  air  drying. 

Clay  No.  53. 

A lavender  colored  clay  from  the  Moss  farm  about  three  miles 
northwest  of  Oxford.  The  chemical  analysis  of  a sample  of  this  clay 
gave  the  following  results: 

ULTIMATE  ANALYSIS, 


Moisture  63 

Loss  on  Ignition  6.66 

Silica  . 70.56 


MISSISSIPPI  A.  & M.  COLLEGE 


71 


Ferric  Oxide  2.27 

Alumina 19.03 

Lime  49 

Magnesia  .13 

Sulphur  Trioxide  19 

RATIONAL  ANALYSIS. 

Clay  Base  48.23 

Free  Silica  41.36 

Fluxing  Impurities 2.89 


This  clay  becomes  plastic  when  mixed  with  25  per  cent,  of  water. 
The  specific  gravity  is  2.45.  The  air-shrinkage  is  6 per  cent. 

Another  sample  of  clay  taken  from  the  same  locality  has  visible 
muscovite  crystals.  The  color  of  the  clay  varies  from  light  yellow  to 
cream.  The  specific  gravity  of  one  sample  was  2.35.  It  becomes 
plastic  when  mixed  with  30  per  cent,  of  water. 


Clay  No.  54. 

This  clay  is  from  the  Miller  farm  five  miles  northwest  of  Oxford. 
It  is  a grayish  white  clay  containing  a high  per  cent,  of  silica.  It  is 
gritty  to  the  taste  and  the  feel.  It  contains  a high  percentage  of  macro- 
scopic quartz  grains.  The  average  tensile  strength  of  its  air  dried 
briquettes  is  90  pounds  per  square  inch.  They  shrink 
is  drying  4 per  cent. 

The  chemical  properties  are  as  follows: 

ULTIMATE  ANALYSIS. 

Moisture  . .73 

Loss  on  Ignition  2.37 

Silica  85.78 

Ferric  Oxide  1.30 

Alumina  6.68 

Lime 48 

Magnesia  14 

Sulphur  Trioxide  .32 

RATIONAL  ANALYSIS. 

Clay  Base  16.93 

Free  Silica  75.53 

Fluxing  Impurities 1.92 


Clay  No.  55. 

This  clay  was  taken  from  the  first  pit  at  the  Oxford 
Brick  and  Tile  Company’s  plant.  The  clay  is  in  the 
topmost  member  of  the  well  section  (See  plate  19). 
It  belongs  to  the  Columbia  and  is  the  basal  member 
of  that  formation.  It  is  brown  in  color  and  has  a 
Fl&  / w?n  se?t?onCk  specific  gravity  of  2.58.  In  water  it  slacks  readily  to 


72 


CLAYS  OF  MISSISSIPPI 


a coarse  grain.  The  average  tensile  strength  of  the  briquettes  when 
dried  rapidly  is  35  pounds  per  square  inch.  It  requires  30  per  cent, 
of  water  to  render  is  plastic.  The  air  shrinkage  is  6 per  cent. 

Grenada  County. 

Geology. — This  county  lies  almost  wholly  within  the  Lignitic- 
Eocene  area.  Doubtless  the  extreme  southwestern  part  of  the  county 
has  the  Buhrstone  for  its  sub-formation. 

The  surficial  formations  are  the  Lafayette,  the  Columbia  and  the 
Bluff  formations.  The  last  named  extends  across  the  western  part  of 
the  county. 

Clay  No.  56. 

A brown  shale  like  clay  collected  from  below  the  bridge  which 
spans  the  Yalobusha  river  at  Grenada.  The  clay  is  light  and  spongy 
and  contains  many  macroscopic  muscovite  crystals. 

The  specific  gravity  of  one  sample  is  1.74.  The  air-shrinkage  is 
4 per  cent. 

A chemical  analysis  gave  the  following  results: 

ULTIMATE  ANALYSIS. 

Moisture 5.91 

Loss  on  Ignition  8.75 

Silica  61.80 

Ferric  Oxide  3.88 

Alumina  16.50 

Lime 00.00 

Magnesia  23 

Sulphur  Trioxide  19 

RATIONAL  ANALYSIS. 

Clay  Base  41.81 

Free  Silica  36.69 

Fluxing  Impurities 5.11 

The  clay  is  not  suitable  for  brick  or  pottery. 

Clay  No.  57. 

A brownish  yellow  brick  clay  from  the  town  of  Grenada.  It 
belongs  to  the  Columbia  or  Brown  loam. 

The  chemical  composition  of  the  clay  is: 

ULTIMATE  ANALYSIS. 

Moisture  . 2.31 

Loss  on  Ignition  2.83 

Silica  - 73.11 

Ferric  Oxide  5.62 

Alumina  10.44 

Lime  1.15 

Magnesia  98 

Sulphur  Trioxide  18 


MISSISSIPPI  A.  & M.  COLLEGE  73 

RATIONAL  ANALYSIS. 

Clay  Base  26.46 

Free  Silica  57.09 

Fluxing  Impurities 7.78 


It  slacks  very  rapidly  to  a medium  grain.  The  specific  gravity 
of  one  sample  was  2.25.  The  air-shrinkage  is  4 per  cent. 

In  burning  the  color  changes  to  red.  Doubtless  a better,  i.  e., 
stronger  brick  could  be  made  with  this  clay  by  mixing  with  it  a small 
amount  of  clay  having  a higher  clay  base. 

Clay  No.  58. 

From  the  public  road  one  mile  east  of  Grenada.  It  is  a very  sandy 
clay  having  a low  percentage  of  clay  substance.  Not  sufficient  clay 
to  be  plastic;  works  much  like  sand.  The  specific  gravity  of  one  sample 
was  2.55.  The  air-shrinkage  is  only  2 per  cent.  In  color  it  is  yellowish 
gray.  The  chemical  composition  is  as  follows: 


ULTIMATE  ANALYSIS. 

Moisture  58 

Loss  on  Ignition  1.45 

Silica  „ 90.33 

Ferric  Oxide  1 .49 

Alumina  . 2.85 

Lime 71 

Magnesia  14 

Sulphur  Trioxide  19 

RATIONAL  ANALYSIS. 

Clay  Base  7.22 

Free  Silica  85.96 

Fluxing  Impurities 2.26 


This  clay  is  too  sandy  for  either  brick  or  pottery  purposes. 

Webster  County. 

Geology. — Webster  county  lies  entirely  within  the  Lignitic-Eocene 
area.  The  eastern  portion  of  the  county  is  occupied  by  the  Flatwoods 
clays  and  the  central  and  western  portions  by  the  Lagrange.  The 
surface  deposit  belongs  to  the  Lafayette  and  the  Columbia. 

Clay  No.  59. 

This  clay  is  from  the  public  road  three  miles  north  of  Mathiston 
on  the  B.  F.  Sanders  farm.  The  clay  occurs  at  the  base  of  a deposit 
of  reddish  clay  which  is  of  a sandy  nature  and  belongs  to  the  Lafayette. 

This  clay  is  plastic  and  has  been  used  by  Mr.  J.  P.  Thomas  of 
Cumberland  in  the  manufacture  of  stoneware.  Mr.  Thomas  mixes 
the  clay  with  a lighter  colored  clay  which  he  obtains  from  near  Clarkson. 
He  operates  a small  pottery,  turning  about  2,000  gallons  per  year  of 
jugs,  jars  and  churns. 


74 


CLAYS  OF  MISSISSIPPI 


The  chemical  composition  of  the  clay  is: 


ULTIMATE  ANALYSIS. 

Moisture  1.47 

Loss  on  Ignition  9.24 

Silica  . 59.82 

Ferric  Oxide  1.26 

Alumina  27.19 

Lime  49 

Magnesia  37 

Sulphur  Trioxide  31 

RATIONAL  ANALYSIS. 

Clay  Base  68.80 

Free  Silica  18.21 

Fluxing  Impurities 2.43 


The  clay  slacks  very  slowly  to  fine  grain.  It  has  a specific  gravity 
of  2.51 . The  tensile  strength  is  68  pounds  for  the  average  and  81  pounds 
for  the  maximum.  The  amount  of  water  required  to  render  it  plastic 
is  25  per  cent.  The  air-shrinkage  is  6 per  cent. 

The  ware  has  a good  strong  body,  but  shows  small  spots  of  iron 
which  would  not  be  present  if  the  clay  were  ground  before  mixing.  The 
brown  slip  glaze  is  used. 

Clay  No.  60. 

In  the  public  road  about  three  and  one-half  miles  north  of  Mathe- 
son  there  is  an  outcrop  of  white  clay  which  on  exposed  surfaces  is  con- 
siderably indurated.  The  plasticity  of  the  unground  clay  is  poor 
but  the  plasticity  increases  with  the  fineness  of  the  grain. 

The  specific  gravity  is  2.31.  In  water  the  clay  slacks  slowly  to 
fine  grain.  The  average  tensile  strength  of  its  air  dried  briquettes 
is  25  pounds  per  square  inch.  It  requires  35  per  cent  of  water  for 
plasticity.  In  air  drying  it  shrinks  4 per  cent.  At  the  temperature 
necessary  to  fuse  cone  6 there  was  no  further  shrinkage.  At  this  point 
the  clay  became  vitrified  and  presented  a firm  white  body  without  spots, 
crazing  or  checks. 

Oktibbeha  County. 

The  sub-formations  of  the  eastern  portion  of  this  county  are  the 
Selma  chalk  and  the  Ripley  marl,  both  of  which  belong  to  the  Cretaceous. 

For  the  western  part  of  the  county  the  Flatwoods  clay  is  the  sub- 
formation. 

The  chief  surficial  formations  of  the  eastern  part  of  the  county  are 
the  Lafayette,  the  Columbia  (Yellow  Loam),  and  the  Selma  residual 
clays  and  sands.  Those  of  the  western  part  of  the  county  are  the  same 
except  that  the  Selma  residual  products  are  replaced  by  those  of  the 
Lignitic.  There  is  also  a much  greater  development  of  the  Lafayette 
and  the  Columbia  formations  in  the  western  part  of  the  county. 


MISSISSIPPI  A.  & M.  COLLEGE 


75 


Clay  No.  61. 

A grayish  clay  from  an  outcrop  of  the  Illinois  Central  railroad, 
•one  and  one-fourth  miles  west  of  Starkville.  The  clay  belongs  to  the 
Flat  woods  formation  of  the  Eocene. 

It  is  a sticky  clay  having  the  characteristic  qualities  of  gumbo. 
The  chemical  composition  of  the  clay  is: 


ULTIMATE  ANALYSIS. 

Moisture  7.20 

Loss  on  Ignition  19.84 

Silica  67.16 

Alumina  12.36 

Ferric  Oxide  5.70 

Lime 1.28 

RATIONAL  ANALYSIS. 

Clay  Base  31.22 

Free  Silica  48.30 

Fluxing  Impurities 6.98 


The  clay  has  a specific  gravity  of  2.48.  It  slacks  very  slowly  in 
water  to  large  grains. 

The  average  tensile  stregth  is  246  pounds  nper  square  inch.  The 
air-shrinkage  is  10  per  cent.  It  requires  25  per  cent,  of  water  to  make 
it  plastic.  The  shrinkage  and  liability  to  check  in  drying  prohibits 
the  use  of  this  clay  for  brick  or  pottery  purposes.  Practical  tests  in 
the  laboratory  have  proven  its  adaptability  for  making  road  ballast. 

Clay  No.  62. 

This  clay  is  from  the  same  locality  and  formation  a few  rods  west 
of  No.  61. 

A chemical  analysis  gave  the  following  results: 

ULTIMATE  ANALYSIS. 


Moisture 4.64 

Loss  on  Ignition  15.04 

Silica  1707 

Alumina  11.62 

Ferric  Oxide  6.30 

Lime 1.29 

RATIONAL  ANALYSIS. 

Clay  Base  29.45 

Free  Silica  52.24 

Fluxing  Impurities 7.59 


The  air-shrinkage  of  this  clay  is  1 1 per  cent.  It  checks  and  cracks 
unless  dried  very  carefully.  Like  No.  61  it  is  a ballast  clay  and  belongs 
to  the  Flatwoods-Eocene  formation. 

Clay  No.  63. 

This  is  a yellow  clay  which  occurs  at  the  base  of  the  Columbia  and 
overlies  the  Selma  chalk.  It  may  belong  to  the  former  or  it  may  be 


76 


CLAYS  OF  MISSISSIPPI 


residual  clay  from  the  latter  in  which  case  it  represents  the  period  of 
erosion  separating  the  two  depositions. 

The  following  is  the  chemical  analysis  of  a sample  taken  from  an 
outcrop  on  the  public  road  one-half  mile  south  of  Starkville. 


ULTIMATE  ANALYSIS. 

Moisture  3.36 

Loss  on  Ignition  19  86 

Silica  57.01 

Alumina  20.86 

Ferric  Oxide  7.70 

Lime 2.44 

RATIONAL  ANALYSIS. 

Clay  Base  52.86 

Free  Silica  25.01 

Fluxing  Impurities 10.14 


The  specific  gravity  of  the  clay  is  2.46.  In  water  it  slacks  slowly 
to  medium  grain.  The  average  tensile  strength  is  158  pounds,  the  max- 
imum is  172  pounds  per  square  inch.  The  air-shrinkage  is  8 per  cent. 
It  requires  about  32  per  cent,  of  water  to  render  it  plastic. 

The  color  of  the  clay  is  changed  to  red  on  burning.  It  is  a good 
quality  of  brick,  clay  and  doubtless  could  be  used  with  success  in  the 
manufacture  of  drain- tile. 

Winston  County. 

Geology. — The  geological  sub-formations  of  Winston  county 
are  the  Lignitic  and  the  Buhrstone.  The  latter  occupies  only  a very 
small  area  in  the  southwestern  part  of  the  county.  As  in  many  coun- 
ties in  the  Lignitic  clay  belt  the  sub-formations  are  largely  concealed 
by  the  more  surficial  deposits  of  the  Lafayette  and  the  Columbia. 

Clay  No.  64. 

This  is  a yellowish  gray  clay  collected  from  an  outcrop  near  the 
top  of  Bevill  Hill  on  the  Octoc-Webster  road.  It  belongs  to  the  Flat- 
woods  sub-division  of  the  Lignitic. 

It  is  a sticky  gumbo  clay  of  fine  texture.  The  clay  contains  a 
large  per  cent,  of  silica  more  than  fifty  per  cent,  of  which  is  uncombined 
and  in  a very  finely  divided  state. 

The  average  tensile  strength  of  its  air  dried  briquettes  is  179 
pounds  while  the  maximum  strength  is  200  pounds  per  square  inch. 

The  specific  gravity  is  2.40.  The  briquettes  in  air  drying  shrink 
10  per  cent.  This  clay  may  be  classed  as  a road  ballast  clay. 

Clay  No.  65. 

On  the  public  road  near  the  Betheaton  Church  there  is  an  outcrop 
of  variegated  clays  in  which  the  prevailing  tints  are  white,  yellow  and 
pink.  This  clay  occurs  at  the  base  of  the  Lafayette. 


MISSISSIPPI  A.  & M.  COLLEGE 


77 


The  clay  has  a specific  gravity  of  2.40.  The  air-shrinkage  is  10 
per  cent.  By  mixing  with  an  amount  of  sand  sufficient  to  decrease 
the  amount  of  shrinkage  this  clay  may  be  rendered  suitable  for  earth- 
enware and  brick. 

Clay  No.  66. 

A white  clay  occurring  in  the  public  road  near  the  Davis  and  White 
saw  mill.  On  the  opposite  side  of  the  draw  from  this  outcrop  there 
is  an  exposure  of  laminated  clays  containing  two  small  seams  of  lignite. 
These  clays  are  at  a higher  level  than  the  white  clay  and  since  the  former 
belong  to  the  Lignitic  it  is  more  than  probable  that  the  latter  also  belongs 
to  that  formation.  The  crests  of  the  ridges  in  this  locality  are  occupied 
by  a thick  layer  of  Lafayette  and  Columbia, 

The  white  clay  has  an  average  tensile  strength  of  only  15  pounds 
per  square  inch.  In  water  it  slacks  slowly  to  medium  grain.  The 
specific  gravity  is  2.42.  The  air  shrinkage  is  only  2 per  cent.  The 
fire-shrinkage  is  3 per  cent.  The  clay  cracks  and  checks  when  burned 
at  the  same  temperature  and  with  the  same  rapidity  of  the  average 
stoneware  clay. 

Clay  No.  67. 

About  two  miles  south  of  Webster  on  the  Macon  road  there  is  an 
outcrop  of  white  clay  containing  pink  and  purple  tints.  The  outcrop 
is  a few  yards  west  of  a church.  The  clay  has  a thickness  of  12  feet. 
It  underlies  a bed  of  lignite  and  belongs  to  the  Lagrange. 

The  impressions  of  leaves  have  been  found  in  the  clay.  The  slopes 
farther  back  from  the  draw  are  occupied  by  Lafayette  and  Columbia. 

This  clay  was  used  for  many  years  by  the  Loyd  family  in  the  man- 
ufacture of  stoneware.  It  is  a very  plastic  clay  having  a specific  gravity 
of  from  2.41  to  2.61.  In  water  it  slacks  slowly  to  fine  grain. 

The  average  tensile  strength  of  its  air  dried  briquettes  is  77  pounds 
and  the  maximum  is  88  pounds  per  square  inch. 

The  amount  of  water  required  to  render  the  clay  plastic  is  25  per 
cent,  of  its  weight.  The  air-shrinkage  is  6 per  cent.  It  vitrifies  to  a 
good  strong  body  at  cone  5.  And  will  take  either  the  salt  or  slip  glaze. 
It  occupies  about  the  same  geological  horizon  as  No.  68  which  doubletss 
belongs  to  the  Lagrange. 

Clay  No.  68. 

On  the  old  Eiland  plantation  one  mile  south  of  the  house  of  Mr. 
J.  A.  M.  Loyd,  on  the  Macon  road,  the  following  section  is  exposed: 


1.  Lafayette  sand  and  clay  4 ft. 

2.  Clay  of  various  tints 15  ft. 


78 


CLAYS  OF  MISSISSIPPI 


A few  rods  south  another  section  is- 
exposed: 

1.  Lafayette  sand  and  clay  6 ft. 

2.  Blue  Clay 4 ft. 

3.  Lignite  3 ft. 

4.  Blue  clay  containing  vegetable  matter  6 ft. 

5.  Clay  and  Ironstone  in  thin  layers.. 4 ft. 

All  but  number  1 of  the  second  section 
is  below  the  first  section.  Number  2 of 
the  first  section  varies  in  color  and  tex- 
ture in  the  various  layers  which  com- 
pose it. 

Mr.  J.  A.  M.  Loyd  who  has  used  the  clay  from  this  outcrop  in  the 
manufacture  of  stoneware  says  that  he  obtains  the  best  results  by 
mixing  the  clay  from  a two-foot  layer  at  the  bottom  with  the  clay  from 
a three-foot  layer  near  the  top. 

The  chemical  analysis  of  a sample  from  the  three-foot  layer  is. 
as  follows: 

ULTIMATE  ANALYSIS. 


Moisture 47 

Loss  on  Ignition  9.24 

Silica  59.82 

Ferric  Oxide  1.26 

Alumina 27.19 

Lime 49 

Magnesia  37 

Sulphur  Trioxide  31 

RATIONAL  ANALYSIS. 

Clay  Base  68.90 

Free  Silica  18.11 

Fluxing  Impurities 2.12 


This  clay  makes  a good  quality  of  stoneware  when  even  the  crude 
methods  of  the  hand  potter  are  employed.  That  with  better  methods 
and  machinery  the  quality  of  the  ware  would  greatly  increase  there 
can  be  little  doubt. 

Clay  No.  69. 

From  the  Homer  Stewart  clay  pit  on  the  Macon-Louisville  road 
about  one-quarter  of  a mile  east  of  the  Stewart  pottery. 

It  is  a yellowish  white  clay  containing  yellow  and  purple  blotches 
and  changing  to  cream  color  when  powdered  and  dampened. 

It  requires  30  per  cent,  of  water  to  render  it  plastic  and  shrinks 
4 per  cent,  in  drying.  The  average  tensile  strength  is  45  pounds  per 
square  inch.  The  specific  gravity  is  2.42. 


Fig.  20.  Section  at  Eiland  Clay  Pit, 
Winston  County. 


MISSISSIPPI  A.  & M.  COLLEGE 


79 


Mr.  Homer  Stewart  uses  this  clay  in  the  manufacture  of  jugs, 
churns,  jars  and  crocks.  He  uses  an  up-draught  kiln  with  a capacity 
of  500  gallons.  His  present  output  is  about  4,000  gallons  per  year. 

He  uses  the  Albany  slip  clay  for  glazing  purposes.  The  clay  be- 
comes vitrified  between  cones  5 and  6.  The  color  of  the  ware  is  light 
red  or  cream.  Its  body  is  firm  and  strong. 

Clay  No.  70. 

A clay  similar  to  the  Stewart  clay  outcrops  near  a creek  bed  on 
the  Ellis  farm,  one-half  mile  south  of  the  Stewart  pottery. 

It  is  a tinted  clay  in  which  the  predominant  colors  are  white  and 
yellow.  In  water  it  slacks  readily  to  medium  grain.  The  specific 
gravity  ranges  from  2.36  to  2.61.  The  average  tensile  strength  of  its 
air  dried  briquettes  is  60  pounds  per  square  inch. 

The  amount  of  water  required  for  plasticity  is  30  per  cent,  and  the 
air-shrinkage  is  5 per  cent.  It  may  be  classed  as  a stoneware  clay  of 
good  quality.  The  fire-shrinkage  is  about  2 per  cent.  The  color  of 
the  burnt  clay  is  variable  from  white  to  light  yellow. 

Lauderdale  County. 

The  Lignitic,  the  Buhrstone  and  the  Claiborne  are  the  sub-for- 
mations of  this  county.  The  first  occupies  the  northeastern  part  of 
the  county.  The  second  occupies  the  remainder  of  the  county  with 
the  exception  of  the  southwestern  corner  which  is  occupied  by  the 
Claibrone. 

The  Lafayette  and  the  Columbia  are  present  as  surficial  formations. 

Clay  No.  71. 

A grayish-white  clay  from  a railroad  cut  one  mile  north  of  Lochart 
which  has  the  following  chemical  composition: 


ULTIMATE  ANALYSIS. 

Moisture 3.14 

Loss  on  Ignition  7.20 

Silica  58.05 

Ferric  Oxide  1.05 

Alumina  27.79 

Lime  2.00 

Magnesia  25 

RATIONAL  ANALYSIS. 

Clay  Base  70.42 

Free  Silica  15.42 

Fluxing  Impurities 3.30 


1 

For  a number  of  years  clay  was  shipped  from  this  point  and  used 
in  Meridian  in  the  manufacture  of  stoneware.  Later  the  Meridian 


Fig.  21. — An  Automatic  Side-Cutter. 


MISSISSIPPI  A.  & M.  COLLEGE 


81 


pottery  was  abandoned.  The  clay  is  now  used  by  the  Wedgewood 
Brothers  in  the  manufacture  of  stoneware.  This  company  owns  a 
steam  pottery  located  near  the  clay  pit.  They  manufacture  a general 
line  of  stoneware  and  have  produced  small  quantities  of  decorated  ware. 

The  clay  has  an  average  tensile  strength  of  98  pounds  and  a max- 
imum strength  of  110  pounds  per  square  inch.  The  specific  gravity 
is  2.44.  The  air-shrinkage  is  4 per  cent. 

Clay  No.  72. 

This  clay  occurs  on  the  farm  of  Mr.  B.  J l.  Brown  about  one-half 
of  a mile  north  of  Lockhart. 

The  clay  has  an  average  tensile  strength  of  78  pounds  and  a max- 
imum strength  of  83  pounds  per  square  inch.  In  water  it  slacks  slowly 
to  a fine  grain.  The  specific  gravity  is  2.38.  It  shrinks  in  drying  4 
per  cent.  It  becomes  plastic  when  mixed  with  30  per  cent,  of  water. 

The  chemical  composition  of  a sample  of  the  clay  is: 


ULTIMATE  ANALYSIS. 

Moisture 4.29 

Loss  on  Ignition  7.74 

Silica  58.21 

Ferric  Oxide  .• 83 

Alumina 27.23 

Lime 65 

Magnesia  41 

RATIONAL  ANALYSIS. 

Clay  Base  69.00 

Free  Silica  16.44 

Fluxing  Impurities 1.89 


Clays  from  Localities  Not  in  the  Foregoing  Clay  Belts. 

The  clays  discussed  under  this  head  are  clays  which  have  been 
collected  from  points  outside  of  the  Potomac  and  Lignitic  Clay  Belts. 

Clay  No.  73. 

A yellowish-white  clay  used  by  the  Biloxi  pottery. 

The  chemical  composition  of  the  clay  is: 

ULTIMATE  ANALYSIS. 


Moisture 1 .48 

Loss  on  Ignition  5.83 

Silica  73.40 

Ferric  Oxide  1.30 

Alumina 17.24 

Lime 32 

Magnesia  41 

RATIONAL  ANALYSIS. 

Clay  Base  43.69 

Free  Silica  46.95 

Fluxing  Impurities 2.03 


82 


CLAYS  OF  MISSISSIPPI 


Clay  No.  74. 

From  the  Eaton  farm  in  Smith  county,  about  five  miles  north  of 
Taylorsville.  It  varies  in  color  from  yellow  to  light  brown.  Is  plastic 
but  somewhat  sticky.  It  is  gritty  to  the  taste. 

A sample  of  the  clay  gave  the  following  chemical  composition: 


ULTIMATE  ANALYSIS. 

Moisture 1.28 

Loss  on  Ignition  6.60 

Silica  .. 71.29 

Ferric  Oxide  3.30 

Alumina 16.78 

Lime 14 

Magnesia  41 

Sulphur  Trioxide  Trace. 

RATIONAL  ANALYSIS. 

Clay  Base  42.52 

Free  Silica  45.55 

Fluxing  Impurities  3.85 


Clay  No.  75. 

From  the  clay  pit  of  the  Laurel  Brick  and  Tile  Company  at  Laurel. 
The  clay  occurs  at  the  base  of  the  Yellow  Loam  which  overlies  the  Grand 
Gulf  in  that  region.  It  is  a bluish  clay  with  streaks  of  yellow. 

The  specific  gravity  is  2.62.  In  water  it  slacks  rapidly  to  a coarse 
grain.  Is  very  gritty  to  taste  and  feel. 

The  average  tensile  strength  of  its  air  dried  briquettes  is  70  pounds 
per  square  inch.  The  briquettes  shrink  in  air  drying  2 per  cent. 

The  chemical  composition  of  the  clay  follows: 

ULTIMATE  ANALYSIS. 


Moisture 1.22 

Loss  on  Ignition  3.66 

Silica  84.86 

Ferric  Oxide  3.96 

Alumina 5.28 

Lime 23 

Magnesia  45 

RATIONAL  ANALYSIS. 

Flay  Base  13.38 

Free  Silica  78.76 

Fluxing  Impurities  4.64 


Clay  burns  to  a bright  red  and  forms  a good  brick  when  properly 
treated. 

Clay  No.  76. 

A non-plastic  white  clay  from  the  gravel  pit  near  Morton,  Scott 
county.  The  plasticity  increases  with  the  fineness  of  the  grain. 

The  chemical  properties  of  the  clay  are: 


Fig.  22. — A Steam  Power  Brick  Machine  of  the  Soft-Mud  Type 


84 


CLAYS  OF  MISSISSIPPI 


ULTIMATE  ANALYSTS. 


Moisture  1.09 

Loss  on  Ignition  8.72 

Silica  60.20 

Ferric  Oxide  3.17 

Alumina  36.72 

Lime 89 

Magnesia  1.83 

Sulphur  Trioxide  Trace. 


Calculated  as  kaolinite  this  clay  contains  enough  alumina  for  a 
clay  base  of  93.39  per  cent.  However,  it  lacks  9.25  per  cent,  of  enough 
silica  to  form  Kaolinite. 

The  percentage  of  fluxing  impurities  is  low,  only  1.39  per  cent. 

Clay  No.  77. 

Was  collected  from  an  outcrop  of  pink  clay  at  Brandon,  Rankin 
county.  It  has  an  unctions  feel  on  exposed  surfaces.  Is  gritty  to  the 
taste. 

The  specific  gravity  of  our  sample  was  2.01.  In  water  it  slacks 
to  a medium  fine  grain.  Briquettes  made  from  the  clay  and  air  dried 
shrink  9 per  cent,  and  have  an  average  tensile  strength  of  50  pounds 
per  square  inch. 

A chemical  analysis  of  the  clay  gave  the  following  results: 

ULTIMATE  ANALYSIS. 


Moisture  1.40 

Loss  on  Ignition  7.36 

Silica  64.79 

Ferric  Oxide  3.58 

Alumina 2 1 .35 

Lime  14 

Magnesia  70 

Sulphur  Trioxide  Trace. 

RATIONAL  ANALYSIS. 

Clay  Base  54.11 

Free  Silica  32.76 

Fluxing  Impurities  4.42 


Clay  No.  78. 

A white  clay  from  Stonington,  Jefferson  county.  It  has  only  a 
moderate  degree  of  plasticity. 

The  chemical  properties  of  the  clay  are: 


ULTIMATE  ANALYSIS. 

Moisture 

Loss  on  Ignition  

Silica  

Ferric  Oxide  

Alumina 

Lime 

Magnesia  

Sulphur  Trioxide  


1.24 

4.08 

78.17 

1.73 

13.23 

.28 

.56 

Trace, 


MISSISSIPPI  A.  & M.  COLLEGE  85 

RATIONAL  ANALYSIS. 

Clay  Base  „ 33.53 

Free  Silica  * 57.87 

Fluxing  Impurities  2.57 


This  clay  occurs  in  an  outcrop  of  Grand  Gulf  at  the  Stonington 
Pottery  and  brick  yard.  Overlying  it  is  about  15  feet  of  brown  loam, 
the  clayey  stratum  of  which  has  been  utilized  for  the  manufacture  of 
brick. 

The  Grand  Gulf  clay  has  a thickness  of  12  or  15  feet  and  has  im- 
bedded in  it  a layer  of  indurated  clay  stone  about  1 foot  thick.  The 
clay  has  been  used  to  a limited  extent  in  the  manufacture  of  stoneware. 

Clay  No.  79. 

A gritty  non-plastic  clay  from  the  same  locality  as  Number  78. 
They  are  both  from  the  Grand  Gulf  formation.  The  clay  varies  in 
color  from  yellow  to  light  brown. 

The  chemical  composition  is  as  follows: 


ULTIMATE  ANALYSIS. 

Moisture  2.14 

Loss  on  Ignition  4.12 

Silica  72.80 

Ferric  Oxide  5.52 

Alumina  11.64 

Lime 44 

Magnesia  1 .03 

Sulphur  Trioxide  Trace. 

RATIONAL  ANALYSIS. 

Clay  Base  29.50 

Free  Silica  59.11 

Fluxing  Impurities  6.99 


Clay  No.  80. 

A plastic;  somewhat  sticky,  grayish  white  clay  from  five  miles 
south  of  Vicksburg. 

The  chemical  properties  of  a sample  of  this  clay  are: 

ULTIMATE  ANALYSIS. 


Moisture  . 3.19 

Loss  on  Ignition  8.26 

Silica  58.50 

Ferric  Oxide  1.93 

Alumina  19.04 

Lime  1.48 

Magnesia  1 .66 

Sulphur  Trioxide  Trace. 


RATIONAL  ANALYSIS. 


Clay  Base  48.25 

Free  Silica  29.29 

Fluxing  Impurities  5.07 


86 


CLAYS  OF  MISSISSIPPI 


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Clay  No.  81. 

A brown  clay  from  the  Loess  formation  at  Vicksburg  used  in  the 
manufacture  of  brick. 

The  following  analysis  * shows  the  chemical  composition  of  the  clay: 

ULTIMATE  ANALYSIS. 


Silica  

Alumina  

Combined  water 
Ferrous  Oxide  ... 
Lime 


60.69 
. 7.95 
. 1.33 
. 3.30 
8.96 


* See  Ann.  Rept.  of  the  U.  S.  G.  S.,  I884. 


MISSISSIPPI  A.  & M.  COLLEGE  87 

Magnesia  4.56 

Potash  1.08 

Soda  1.17 

Titanic  Acid  52 

Carbon  Dioxide  9.63 

Fluxing  Impurities  19.44 


When  properly  handled  this  clay  makes  a good  brick.  The  dry 
or  semi-dry  press  method  of  molding  gives  good  results.  Great  care 
must  be  exercised  in  burning  the  brick.  On  account  of  the  presence 
of  a large  per  cent,  of  lime  the  burning  period  must  be  greatly  extended. 
While  the  majority  of  the  Yellow  Loam  brick  clays  may  be  water- 
smoked  and  burnt  in  from  seven  to  ten  days,  some  of  the  Loess  clays 
require  as  many  as  nineteen  days. 

Clay  No.  82. 

A lavender  colored  clay  from  an  outcrop  one  mile  east  of  Brandon, 
Rankin  county.  It  is  a plastic  tough  clay  of  coarse  grain. 

The  chemical  composition  of  the  clay  is: 

ULTIMATE  ANALYSIS. 


Moisture 

Loss  on  Ignition  . 

Silica  

Ferric  Oxide  

Alumina 

Lime 

Magnesia  

Sulphur  Trioxide 


7.53 
. 8.72 
60.20 
. 3.17 
.17.28 
. .89 

. 1.83 
. Trace. 


RATIONAL  ANALYSIS. 


Clay  Base  43.79 

Free  Silica 33.69 

Fluxing  Impurities  5.89 


Clay  No.  83. 

A yellow  clay  from  the  Smith  farm  at  Barnett  has  the  following 
chemical  composition: 


ULTIMATE  ANALYSIS. 


Moisture 5.55 

Loss  on  Ignition  13.80 

Silica  38.75 

Alumina 22.83 

Ferric  Oxide 3.14 

Lime 14.25 

Magnesia  1.01 

Sulphur  Trioxide  Trace. 


88 


CLAYS  OF  MISSISSIPPI 
RATIONAL  ANALYSIS. 


Clay  Base  57.86 

Free  Silica.. 3.72 

Fluxing  Impurities  18.40 


About  8 feet  of  the  clay  is  exposed  at  the  point  where  the  clay  was 
collected.  Borings  have  been  made  reaching  a depth  25  feet  below 
the  bottom  of  the  outcrop  without  going  to  the  bottom  of  the  clay  bed. 

The  clay  in  the  upper  part  contains  large  numbers  of  small  shells 
and  some  selenite  crystals.  These  two  substances  are  the  source  of 
the  lime  as  the  sample  was  taken  from  the  upper  part  of  the  clay  bed 
The  clay  in  the  lower  part  seems  to  be  free  from  shells  and  selenite. 


